Best IR Thermometer

Updated December 11th, 2019

Don’t be fooled. Super cheap “budget grade” IR thermometers do not provide the same accuracy and overall performance as their much more expensive professional grade counterparts.

But is the extra cost of a professional grade unit worth it? What should you be looking out for to determine whether you can get away with buying a budget model or whether you’ll have no other option but to spend more on a more professional grade unit? Let’s take a look.

Features

Make an informed purchase. These are the features you should look out for when shopping for an IR thermometer.

Emissivity

You’re in your kitchen performing a very simple but exciting science experiment to test the accuracy of your brand new IR thermometer – you’re boiling water inside an aluminum pot. You already know that the boiling point of water is 212° F so you know that inside the pot, the water is boiling at 212° F. You also know that the pot itself must be at a temperature very close to 212° F. You grab your newly purchased IR thermometer, scan the water and the thermometer displays a reading of 212° F. Great! It works! You scan the side of the pot and the thermometer displays a reading of 100° F.

Puzzled, you scan again – 100° F. What’s the problem? You know the side of the pot is at a temperature very close to 212° F, if not right at 212° F. Why is the thermometer telling you otherwise?

The answer? Emissivity.

That word – emissivity - sounds complicated doesn’t it? Unfortunately, you’ll absolutely have to understand it or at least understand how it applies to IR thermometers for you to pick the right thermometer for your application. An explanation follows below.

What is emissivity?

Everything’s made up of atoms. At temperatures above absolute zero these atoms move. The movement of these atoms gives off IR radiation. An IR thermometer detects this radiation.

This is how an IR thermometer works – it detects the amount of IR radiation surface materials emit at different temperatures.

Here’s the problem. The amount of IR radiation a surface material emits only tells half the story of the material’s temperature. For the IR thermometer to give an accurate temperature reading it needs to also know how efficiently the material can emit the radiation. If it’s a poor emitter this needs to be compensated for. Likewise, if it’s a good emitter this needs to be compensated for also.

And so, an IR thermometer needs two pieces of information to take an accurate reading:

The amount of IR radiation emitted by the material
The efficiency with which the material can emit IR radiation

Emissivity is the term we use to describe that second piece of information - the efficiency with which a material can emit IR radiation.

IR thermometers – not as simple to use as they seem

You know that an IR thermometer detects the amount of IR radiation a surface material emits. You know that it needs to “know” the efficiency with which the material can emit that radiation before it can take an accurate reading – it needs to “know” the material’s emissivity. So how does it come to “know” the material’s emissivity? Is it detected automatically?

Unfortunately, it isn’t. Each time you want to measure the surface temperature of a particular object it will be up to you to

Determine the identity of the material that comprises the object’s surface
Look up the material in an emissivity table
Input the number listed next to that material in the emissivity table into the thermometer

Only after completing these 3 steps will you be able to obtain an accurate reading.

Fixed Emissivity

All of this sounds a bit complicated, doesn’t it? It is in fact, likely a far cry from what you might expect to be able to do with an IR thermometer – to be able to point it at any object and instantly get an accurate temperature reading with no further work required.

And many IR thermometer manufacturers would agree with you. Their solution? Fixed emissivity.

You see, many common household materials have an emissivity at or close to 0.95 (food, water, paint and paper are some examples). IR thermometers with a fixed emissivity of 0.95 (the chosen value for all IR thermometers with fixed emissivity) are able to measure the temperature of all of these items quite accurately.

But then you run into a scenario like the one described earlier. You aim your fixed emissivity IR thermometer at a highly reflective surface (the side of a polished aluminum pot), and there’s a good chance it’s going to give you a temperature reading that’s nowhere close to the actual temperature of the surface.

Manufacturers of budget IR thermometers are banking on the fact that you’re unlikely to use their thermometers to measure the temperature of these types of surfaces. If and when you do, an IR thermometer with fixed emissivity will not be able to take an accurate temperature reading of the surface.

Adjustable Emissivity

It is our strong recommendation that you buy an IR thermometer with adjustable emissivity – such a thermometer will allow you to input a particular emissivity value into the thermometer before taking a reading.

An IR thermometer with adjustable emissivity allows you to get an accurate temperature reading of any surface, no matter what material the surface is comprised of.

Back to the original problem – water inside an aluminum pot

The water inside the pot had an emissivity value close to 0.95 – the default setting for IR thermometers that feature adjustable emissivity and the only setting for IR thermometers that feature fixed emissivity. The side of the aluminum pot has an emissivity value much different than that of water – close to 0.1 – the lowest emissivity setting for thermometers that feature adjustable emissivity.

Let’s say you purchase a budget IR thermometer with a fixed emissivity setting of 0.95. If this were the case there would be no way for you to adjust settings on the thermometer to accurately measure the temperature of the side of that aluminum pot (which has an emissivity value close to 0.1).

If you purchase a more expensive IR thermometer with adjustable emissivity you would need to look up the emissivity of polished aluminum in a table, input the correct value (0.1) into the thermometer, and only then would you be able to take an accurate reading of the side of the pot.

Note

There is a way to get around the limitations of a fixed emissivity IR thermometer. You can place non-reflective tape (with an emissivity value of 0.95) over the surface you need to measure and then take a reading of the area covered by the tape. While doing so will give you a more accurate reading without adjusting emissivity, this method has several shortcomings:

The surface you need to measure may already be very hot or very cold, making it difficult to put tape over it.
The surface you need to measure may be out of reach, making it impossible to put tape over it.
The surface you need to measure may be comprised of a material that tape won’t stick to.
The tape itself has a limited surface area. The spot the thermometer is measuring may be larger than the width of the tape, which will also give inaccurate readings.
You need to wait several minutes (some manufacturers recommend waiting 30 minutes) for the tape to adjust to the temperature of the surface before taking a reading.

The bottom line? There’s absolutely no need to have to worry about the limitations of this tape trick in the first place - just buy a thermometer with adjustable emissivity.

Accuracy

Reading down the spec sheet of a typical IR thermometer you’ll see accuracy listed in the same table as weight, size, and operating temperature, among other things.

The thermometer’s weight is a hard and fast rule. The thermometer weighs a certain number of ounces or grams and this requires no further explanation.

Its size is also a hard and fast rule. The thermometer has certain dimensions measured in inches or centimeters and this requires no further explanation.

The range of temperatures it can measure – its operating temperature - is also a hard and fast rule – the thermometer will work within the specified range and it will not work outside of the specified range. This requires no further explanation.

But what about accuracy? The accuracy specification is usually listed as either a plus or minus number or a percentage. The Fluke 62 Max+, for example, is listed to be accurate within plus or minus 2° F or 1% of the measured reading - whichever is greater – at temperatures at or above freezing (32° F).

Manufacturers list these numbers like they’re a hard and fast rule - just like size, weight, and operating temperature. But are things really this simple when it comes to IR thermometer accuracy? Can accuracy really be treated like and listed in the same table as every other specification – as a given value with no further explanation? We don’t believe it can.

A closer look at IR thermometer accuracy

You see, many IR thermometers are not nearly as accurate as their manufacturers claim that they are, at least not

when they first show an initial reading and
when you use them under certain conditions

To explain what we mean by this we need to first introduce another specification you might run into when reading through a typical IR thermometer’s spec. sheet - response time. This number is usually listed in milliseconds. The Fluke 62 Max+, for example, has listed response time of less than 300 ms. Next to this time, listed in parentheses is “95% of the reading”. This means that Fluke claims that you can obtain a reading within 5% of the final measured reading within 300 ms of a trigger pull. We tested the 62 Max+ and found this to be true. We pulled on its trigger and almost immediately the thermometer’s LCD displayed a reading within 5% of the final measured reading.

Here’s the problem. The Fluke 62 Max+ is a professional grade IR thermometer. It’s a really good thermometer – one of the best IR thermometers on the market.

Many IR thermometers on the market or not professional grade. They do not read the final measured value nearly as fast. So while the accuracy of the 62 Max+ may look very similar to that of much less expensive models if you compare their specifications side by side and take them at face value – these specifications don’t tell the whole story.

Take the Etekcity 630 as an example. It normally retails for less than a quarter of the price of the Fluke 62 Max+. It’s listed to be accurate to within 2% of the measured reading at temperatures above 212° F with a response time of 500 ms.

Now, you may compare these two models (the Fluke and the Etekcity) side by side and say 2% vs 1% for accuracy isn’t much of a difference. And that 500 ms vs 300 ms isn’t much of a difference either.

But here’s the thing. First of all, the Etekcity 630 doesn’t really have a response time of 500 ms. It takes about that long for the LCD screen to turn on but it doesn’t display an actual reading until at least 2 seconds after you pull its trigger.

At this point – 2 seconds later – it shows an initial reading. At lower temperatures (below 200° F) this initial reading is quite close to the final reading – the same as is true for the Fluke. But at higher temperatures (over 200° F) the 630 often gives an initial reading more than 10, 20° F away from the final reading. It then takes several more seconds for it to settle on a final reading.

But the fun doesn’t stop there. After it settles on a final reading it often bounces up or down to a different reading 10 or 20 degrees above or below the actual temperature.

This type of behavior is typical for a budget IR thermometer. And this is exactly the type of behavior you won’t have a clue is a possibility when reading and comparing manufacturer specifications for accuracy and response time.

So, in summary: be wary of manufacturer specifications for accuracy. Budget thermometers often exhibit the following behavior:

They give a much different initial reading than their final reading at certain temperatures.
They take a long time to settle on the final measured reading at certain temperatures.
They may “bounce” between reading the actual temperature and some other temperature. Which is the correct temperature? During testing we were well aware of the actual surface temperature of the surfaces we were taking readings of. We also had more expensive models to compare cheaper thermometers to. You won’t have the same luxury should you purchase only one budget IR thermometer for yourself. So think about whether this type of behavior will be acceptable to you.

Distance to Spot Ratio

An IR thermometer measures the surface temperature of a circular area – a spot. The size of the spot changes depending on how far the thermometer is held away from the surface.

The further the thermometer is moved away from the surface, the larger the area being measured.

The closer the thermometer is moved toward the surface, the smaller the area being measured.

An IR thermometer’s distance to spot (D/S) ratio describes this phenomenon – it describes the relationship between the distance the thermometer is held away from the surface and the size of the spot.

The first number of the ratio represents the distance the thermometer is held away from the surface. The second number represents the spot size. For example, a thermometer with a 10:1 D/S ratio will measure a spot 1 inches in diameter when held 10 inches away from the surface. The spot size will grow to 2 inches when the thermometer is held 20 inches away from the surface, and so on and so forth.

Here’s why D/S ratio is important – high D/S ratio advantages

1. The higher the D/S ratio, the smaller the size of the spot being measured at any distance.

For example, a thermometer with a 50:1 D/S ratio held 100 inches away from a surface will measure a spot with a 2 inch diameter. A thermometer with a 10:1 D/S ratio, held the exact same distance away - 100 inches away from the target - will measure a spot with a much larger 10 inch diameter.

The higher D/S ratio thermometer keeps this small spot advantage no matter how far away you hold each thermometer from the surface. If you move both thermometers closer to the surface – say 50 inches away – the 50:1 model will have a spot size of 1 inch (still smaller) while the 10:1 model will have a spot size of 5 inches (still larger). If you move both thermometers further away – say 200 inches away – the 50:1 model will have a spot size of 4 inches (still smaller) while the 10:1 model will have a spot size of 20 inches (still larger).

If you need to measure the temperature of small spots at any distance you’ll need an IR thermometer with a high D/S ratio.

2. The higher the D/S ratio, the further you can be from the spot you want to measure.

A thermometer with a 50:1 D/S ratio can be held 50 inches away from the target to measure a 1 inch diameter spot. A thermometer with a 10:1 D/S ratio would need to be held 10 inches away to measure the same size spot.

If you need to measure a relatively small spot from a large distance away from the surface then you’ll need an IR thermometer with a high D/S ratio.

D/S ratio is not a deal maker or a deal breaker

Most applications will not require an IR thermometer with a D/S ratio greater than 10:1. You can always move closer to the surface with a low D/S ratio thermometer to obtain a small spot size (this negates advantage #1 above). Few applications require you to measure a very small spot size from far away (advantage #2 above).

At this point you may be thinking that

there’s really no disadvantage to buying a high D/S ratio thermometer and
there’s no apparent advantage to buying a low D/S ratio thermometer

So why would you ever buy a low D/S ratio thermometer over a high D/S ratio thermometer?

The answer – price. Manufacturers know that high D/S ratio thermometers are only required for very specific professional work and price them accordingly. High D/S ratio IR thermometer pricing starts at around $200.

Lasers

Above we discussed how the size of the spot that you’re measuring changes as you move toward or away from your target. But how do you know the exact location and size of the spot at any particular distance?

The answer? Lasers.

Most IR thermometers come equipped with either one or two lasers. The more lasers, the better.

Single laser thermometers only show you the location of the spot you’re measuring. The laser points to either the center, the bottom, or the top of the spot being measured. It’s up to you to determine how far away you are from the surface and thereby determine the size of the area you’re measuring.

Dual laser thermometers not only show you the location but also the size of the spot. As you move toward the target the lasers come closer together (as the spot gets smaller). Directly in between the two lasers is the spot being measured. As you move away from the target the lasers move farther apart (as the spot gets larger).

Everything Else

Temperature Range

An IR thermometer can only read temperatures that fall within a certain (manufacturer specified) range. This range varies from model to model but normally falls between about -20° F and around 1000 to 1200° F.

The specified range for the vast majority of IR thermometers on the market will be more than adequate for the majority of applications no matter how “limited” that range is. That is because even units with a more “limited” range still have a very wide range of several hundred degrees Fahrenheit.

Only concern yourself with an IR thermometer’s temperature range

if you’re buying one for professional use and you need to measure the temperature of materials that exceed certain known extreme temperatures.
if you’re considering buying an extremely cheap unit – these units are the only IR thermometers on the market that have a range limited to the point where you really need to pay attention to it before making a purchase. When looking at extremely cheap units look at their temperature range and consider whether that range will be sufficient for your application.

Overall Experience and Ease of Use

Your overall experience using an IR thermometer and overall ease with which you end up using it will vary greatly depending on the following 4 factors:

The size and clarity of the temperature read-out.

Some IR thermometers have large easy to read LCD displays while others have much smaller more difficult to read displays. We also found that some displays had a better viewing angles than others.

How quickly the device activates – response time.

Most IR thermometers have a manufacturer specified response time less than 1 second - pull the trigger and the thermometer displays the measured temperature in less than 1 second. Interestingly, we found that not all thermometers activate as quickly as their manufacturer claims that they do. The Etekcity 630, for example, has a manufacturer specified response time of 500 ms. The unit we tested took over 2 seconds to activate – more than 4 times slower than what is claimed by the manufacturer.

How quickly the device shuts off after taking a reading.

You pull the thermometer’s trigger to activate it. While you have the trigger pulled the thermometer is constantly updating temperature information on its LCD screen. Only when you release the trigger is a final temperature displayed on the screen. But for how long? Some units display this final temperature for over 20 seconds. Some for as little as 5 seconds.

You may need to write down temperature data as you collect it. To write it down you need to release the trigger and when you do, the longer the information stays on the screen, the better.

How difficult it is to select different settings.

For each of the thermometers we researched and tested, we not only looked at which extra features they had or didn’t have but we also took a close look at how well these features were implemented. For example, the Etekcity 630 requires you to hold down a button for 3 seconds to switch between degrees Celsius and degrees Fahrenheit. Doing so, also turns the backlight on or off. This is an example of a poor implementation of this extra feature.

Extra Features

An IR thermometer can be used for more than just measuring one temperature at one pinpoint location. Holding down the trigger of more advanced units will allow you to scan over an area and determine the average, maximum, and minimum temperature of the region that was scanned.

Some units will also allow you to scan one object and then another and then show you the difference in temperature between the two surfaces.

Other common extra features include

A backlight to illuminate the thermometer’s LCD display in low light applications.
A low and high temperature alarm. The unit will beep or a message will flash on the display when the temperature of the scanned surface is above or below a set temperature.
The ability to switch between degrees Celsius and degrees Fahrenheit.

Battery

Not all of IR thermometers use the same type of battery. During testing we preferred units that used a AA battery instead of a 9V battery. Why? Replacing the batteries of 9V battery units required managing wires – making sure they wouldn’t pinch between the battery lid and the thermometer - the same wasn’t required for AA battery units.

etekcity 630 battery compartment — 9V battery compartment (Etekcity 630)

Size and Shape

Depending on how you plan on using your IR thermometer, it’s size and shape may or may not be important to you. If you plan on using it very infrequently, you really don’t need to concern yourself with its size or ergonomics. A large thermometer that doesn’t fit your hand well will work just fine. But, if you do plan on using it often and/or for professional work, consider getting a unit that’s comfortable to hold and compact in size.

Durability and Warranty

We also took a close look at the build quality and warranty included for each IR thermometer we tested.

Top 3

Our reviews for the three best IR thermometers on the market.

#1 The best overall

Fluke 62 MAX+

SEE PRICE ON AMAZON

Emissivity

The Fluke 62 MAX+ features adjustable emissivity for maximum accuracy no matter what material you’re scanning. Yes, you will have to identify the material you’re scanning, look up its emissivity in a table, and input the correct emissivity value into the thermometer each time you take a reading (of a different material). But these are required steps for taking an accurate reading with an IR thermometer.

An IR thermometer that doesn’t require you to do this work – a unit with fixed emissivity – isn’t doing you any favors. Such a thermometer is guaranteed to be extremely inaccurate taking readings of any material that doesn’t have an emissivity value of 0.95 – the fixed value that most fixed emissivity thermometers are set to.

The 62 MAX+ won’t have this problem. It is guaranteed to be accurate no matter what. Just remember to adjust its emissivity setting when necessary.

Accuracy

Like all other IR thermometers we tested, the 62 MAX+’s manufacturer specified accuracy is maximized near room temperature, reduced at mid to high temperatures, and greatly reduced at extremely low or extremely high temperatures.

Below 14° F the thermometer’s accuracy is only plus or minus 6° F. Accuracy between 14° F and 32° F is plus or minus 4° F. Accuracy above 32° F is plus or minus 2° F or 1% of the reading, whichever is greater.

Our hands-on testing of the MAX+ revealed these numbers to be accurate (no pun intended).

Temporary Accuracy

Earlier we talked about IR thermometer accuracy being more than just a number. We talked about how several IR thermometers we tested exhibited strange behavior when taking readings – behavior that made it difficult to take accurate readings quickly and with complete certainty.

The Fluke 62 MAX+ exhibited none of this behavior. During testing, it displayed temperature readings almost instantaneously upon trigger pulls. Many other thermometers we tested would immediately turn on (with their LCD display active), but many would take at least a few seconds to display temperature readings. Often these initial readings were nowhere close to the final readings these thermometers would settle on after keeping their triggers pulled for a few seconds.

The 62 MAX+ also did not exhibit any of the “bouncing” behavior we discussed earlier. It always gave only one final reading – the actual reading of the actual temperature.

Distance to Spot Ratio

The 62 MAX Plus has a distance to target (D/S) ratio of 12:1. The first number of the ratio (12) represents the distance between the thermometer and the surface. The second number (1) represents the size of spot on the surface that is being measured.

This means that if you hold the 62 MAX+ 12 inches away from the surface you want to measure, it will measure a spot with a 1 inch diameter on the surface. Moving it closer or farther away from the surface will affect the spot size according to the D/S ratio.

For example, holding the 62 MAX+ 24 inches away from the surface will increase the spot size to 2 inches. Holding it 36 inches away from the surface will increase the spot size to 3 inches, and so on and so forth.

During testing, we found the 62 MAX+’s D/S ratio to be more than acceptable for the vast majority of applications. Units with higher ratios did provide

Smaller spot sizes
The ability to measure smaller spots from further away

But we don’t find these advantages to be necessary for most applications. And we definitely don’t feel that paying for a higher D/S ratio thermometer is worth it for most users. If you do absolutely need an IR thermometer with a high D/S ratio our recommendation would be the Fluke 572. It provides a whopping 60:1 D/S ratio. But be warned, it also carries a hefty price tag. It normally retails for over $700.