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Best Infrared Thermometer: 15 Temp Guns Tested for Accuracy
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More head-to-head tests from Tools & Workshop / Measuring & Inspection
Fifteen infrared thermometers, $8 to $245, measured against a contact
thermometer carrying a certificate of calibration accurate to within a tenth of
a degree. Each gun read the same five targets: a concrete floor stabilized at
69.4°F, a steel plate held on a hot plate at 386°F for four hours, steel left in
a -16°F freezer overnight, a glossy steel plate at 69°F, and a polished aluminum
wheel at 71.3°F. Reading speed and distance-to-spot ratio were measured
separately, and display legibility was assessed subjectively in direct sunlight.
The five accuracy errors add up to a single cumulative figure, and it does not
track price. The $245 Fluke does finish on top at 8.8°F cumulative — but the $63
Putt River is next at 12.6°F, the $9 T600 is third at 18.0°F, and the two Klein
Tools guns at $65 and $104 land near the bottom at 31.6°F and 33.3°F. Every gun
here is made in China, including the Fluke.
At $245 the most expensive gun here, with a 12:1 spot ratio and only low and high emissivity presets rather than a numeric setting. It was never worse than fourth in any round: first on shiny steel at 2.4°F, tied first on polished aluminum at 0.1°F, third in the freezer at 2.6°F, 3.0°F on the hot plate, and second-fastest at 0.3 seconds. Lowest cumulative error at 8.8°F. Very easy to read in direct sunlight.
Nine dollars, rated -58°F to 1,112°F, with auto-off to preserve battery life and no adjustable emissivity. It tied for second on concrete at 0.2°F of error, took second on the hot steel plate at 1.5°F, and read in 1.17 seconds. Cold is its weak spot: 11.3°F off in the freezer. Third-lowest cumulative error at 18.0°F, tied for second overall.
Thirty-eight dollars, -40°F to 2,732°F, dual laser, emissivity adjustable from 0.1 to 1.0, and a 50:1 distance-to-spot ratio — over four times the reach of the Fluke. It won the concrete test at 0.1°F of error and read in 0.7 seconds. It struggled badly with the hot steel plate at 22°F low, and its dark display is as hard to read in sun as the FKM. Tied for second.
The least expensive gun in the group at $8, rated -58°F to 932°F with a claimed accuracy of ±1.5% and a 12:1 distance-to-spot ratio. Emissivity is fixed. It was respectable on concrete at 1.7°F of error, but it collected the largest cumulative error of the field at 38.4°F, driven by an 11.7°F miss on shiny steel and 12.7°F on the hot plate. Its display is one of the easier ones to read in direct sunlight.
Seventeen dollars, with a claimed ±1.5% accuracy, a 500 ms response time, and selectable minimum, maximum, or average readings. It owns the freezer test outright at 0.4°F of error, the best cold result of the group, but it was 4.5°F low on concrete and 14.3°F low on the hot plate. Readable in direct sunlight.
Nineteen dollars, -58°F to 1,112°F, claimed ±2% accuracy, 12:1 spot ratio, 500 ms response. Consistently mid-pack and never disastrous: 1.0°F on concrete, 0.5°F on the aluminum wheel, 5.0°F on the hot plate, for a cumulative 19.0°F. Adjusting emissivity away from 0.95 made its shiny-surface accuracy worse, not better. The display is effectively unreadable in direct sunlight.
Nineteen dollars with emissivity adjustable from 0.1 to 1.0, a 12:1 spot ratio, and a -58°F to 1,112°F range. It has the clearest display in direct sunlight of any gun here, earning the best possible visibility rating, and tied the Fluke for first on polished aluminum at 0.1°F. The hot plate undid it: a 24°F miss, the largest error recorded in that round.
Thirty dollars, -58°F to 1,112°F, with a 12-point laser array instead of a single dot and emissivity adjustable from 0.1 to 1.0. Includes a carrying case. Strong in the cold at 3.6°F of error and quick at 1.17 seconds, but 20.5°F off on the hot plate and 6.3°F off on shiny steel, for a 34.1°F cumulative total. Its dark display is unreadable outdoors in sun.
Thirty-six dollars, with the broadest range of the budget guns at -58°F to 1,472°F, a sub-half-second response, a 12:1 spot ratio, and a carrying case. Fast at 1.12 seconds and within 1.8°F on concrete, but it would not return a usable reading inside the freezer at any emissivity setting, so it is not suited to cold work. Its dark display is nearly impossible to read in sunlight.
Forty-eight dollars, -58°F to 2,552°F, 30:1 spot ratio, claimed ±2% accuracy, with a warning that low battery levels can skew readings. Third on the aluminum wheel at 0.2°F and within 0.3°F on concrete, but 9.0°F off on shiny steel and by far the slowest gun tested at 3.44 seconds per reading. Best of the dark-display group for sunlight readability.
The Harbor Freight entry at $50, with a 20:1 spot ratio, a 2.1 in color screen, and adjustable emissivity. It tied for second on concrete at 0.2°F and did better than average in the freezer at 5.7°F. On shiny steel, an emissivity setting of 0.8 worked better than the 0.95 default but still left an 8.9°F error. The color screen is very challenging to see in direct sunlight.
Sixty-three dollars, -58°F to 2,876°F, a 30:1 spot ratio, and a built-in flashlight. It won the hot steel plate test at 1.2°F of error and was second only to the Fluke on shiny steel at 2.7°F, finishing with the second-lowest cumulative error of the group at 12.6°F. Slower than average at 1.79 seconds, and its display is very difficult to read in sunlight.
Sixty-five dollars, -22°F to 752°F, 12:1 spot ratio, dual laser targeting, and a carrying pouch. Third on the hot plate at 1.6°F and the third-fastest gun at 0.6 seconds, but it struggled everywhere else: 3.3°F on concrete, 10.0°F in the freezer, and the worst shiny-steel result of the field at 12.1°F. Cumulative error 31.6°F. Easy to read in direct sunlight.
Eighty-six dollars, -22°F to 752°F, with the narrowest reach here at a 10:1 spot ratio and emissivity locked at 0.95. Second in the freezer at 1.9°F, within 0.7°F on concrete, and 5.0°F off on shiny steel, for a cumulative 19.0°F — better than either Klein Tools gun and both Klein models cost less or the same. Display readability sits between the dark screens and the best of the group.
The most expensive non-Fluke gun at $104, rated -40°F to 1,200°F with a 20:1 spot ratio, emissivity adjustable from 0.1 to 1.0, a carrying pouch, and a drop rating of nearly 10 ft. By far the fastest reading of any gun at 0.2 seconds, and 1.3°F on the aluminum wheel, but 11.5°F off in the freezer and 9.7°F off on the hot plate for a 33.3°F cumulative error. Easy to read in sunlight.
Price
Lower is better
Prices run more than thirty to one, from the $8 Sunot to the $245 Fluke, with ten of the fifteen guns under $50. Every one of them is made in China, so price here buys sensor quality, spot ratio, and display legibility rather than country of origin.
Cumulative Temperature Error Across Five Tests (°F)
Sum of the error from all five accuracy tests; lower is better
Adding the five accuracy errors together separates the consistent guns from the ones that were lucky in a single round. The Fluke totals 8.8°F, the Putt River 12.6°F, and the $9 T600 18.0°F. The $86 Milwaukee ties the $19 Sarotti at 19.0°F, and both Klein Tools guns finish worse than every thermometer under $20 except the Sunot.
Full results table
Rank
Product
Result
1
Fluke
8.80
2
Putt River
12.60
3
T600
18
4
Sarotti
19
5
Milwaukee
19
6
Surer
25.10
7
Ames Instruments
26.40
8
ThermoPro
27.90
9
Klein Tools IR5
31.60
10
Viver
32.30
11
Klein Tools IR10
33.30
12
FKM
34.10
13
Sunot
38.40
Error on 69.4°F Concrete Floor (°F)
Absolute deviation from the calibrated probe; lower is better
Concrete at 69.4°F is the easiest surface in the group — matte, dull, and close to the 0.95 emissivity these guns default to. The Viver led at 0.1°F, with the $9 T600 and the $50 Ames Instruments tied at 0.2°F. The $17 ThermoPro was the outlier at 4.5°F low, worse than the $8 Sunot.
Full results table
Rank
Product
Result
1
Viver
0.10
2
T600
0.20
3
Ames Instruments
0.20
4
Surer
0.30
5
Milwaukee
0.70
6
Fluke
0.70
7
Sarotti
1
8
Putt River
1.30
9
FKM
1.60
10
Sunot
1.70
11
Mestic
1.80
12
Klein Tools IR10
2.30
13
Klein Tools IR5
3.30
14
ThermoPro
4.50
Error on 386°F Steel Plate (°F)
Absolute deviation from the calibrated probe; lower is better
Steel held at 386°F for four hours is where the field spreads out the most, from 1.2°F to 24°F. The Putt River took it at 1.2°F, the T600 second at 1.5°F, and the Klein Tools IR5 third at 1.6°F. The Kaizen and the Viver, both strong elsewhere, collapsed here at 24°F and 22°F low.
Full results table
Rank
Product
Result
1
Putt River
1.20
2
T600
1.50
3
Klein Tools IR5
1.60
4
Fluke
3
5
Sarotti
5
6
Surer
5.90
7
Milwaukee
7.50
8
Ames Instruments
9.50
9
Klein Tools IR10
9.70
10
Sunot
12.70
11
Mestic
13.80
12
ThermoPro
14.30
13
FKM
20.50
14
Viver
22
15
Kaizen
24
Error on -16°F Frozen Steel (°F)
Absolute deviation from the calibrated probe; lower is better
Two pieces of steel sat in a -16°F freezer for twelve hours. The ThermoPro, mediocre everywhere else, was nearly perfect here at 0.4°F, ahead of the Milwaukee at 1.9°F and the Fluke at 2.6°F. Cold is the T600's one real weakness at 11.3°F, and the Klein Tools IR10 was worse still at 11.5°F. The Mestic never produced a usable reading at all, across repeated attempts and every emissivity setting.
Full results table
Rank
Product
Result
1
ThermoPro
0.40
2
Milwaukee
1.90
3
Fluke
2.60
4
FKM
3.60
5
Ames Instruments
5.70
6
Putt River
6.60
7
Viver
6.70
8
Sarotti
7.30
9
Kaizen
9.50
10
Sunot
9.70
11
Surer
9.70
12
Klein Tools IR5
10
13
T600
11.30
14
Klein Tools IR10
11.50
15
Mestic
0 (DNF)
Error on Glossy Steel Plate (°F)
Absolute deviation from the calibrated probe; lower is better
Smooth, shiny finishes are the hardest thing an infrared thermometer is asked to read, and the whole field is off by degrees rather than tenths. The Fluke led at 2.4°F, the Putt River at 2.7°F, the Viver at 3.0°F. Dialing emissivity away from 0.95 rarely helped: only the Ames Instruments improved on the default, and it was still 8.9°F out at 0.8.
Full results table
Rank
Product
Result
1
Fluke
2.40
2
Putt River
2.70
3
Viver
3
4
Kaizen
3.80
5
T600
4.30
6
ThermoPro
4.90
7
Milwaukee
5
8
Sarotti
5.20
9
FKM
6.30
10
Mestic
6.40
11
Klein Tools IR10
8.50
12
Ames Instruments
8.90
13
Surer
9
14
Sunot
11.70
15
Klein Tools IR5
12.10
Error on Polished Aluminum Wheel (°F)
Absolute deviation from the calibrated probe; lower is better
A polished aluminum wheel at 71.3°F is a more realistic shiny-surface job than a lab plate, and most of the field handled it far better. The Kaizen and the Fluke tied for first at 0.1°F, with the Surer at 0.2°F. The Klein Tools IR5 was last again at 4.6°F, and the Milwaukee gave up 3.9°F despite being one of the better guns overall.
Full results table
Rank
Product
Result
1
Kaizen
0.10
2
Fluke
0.10
3
Surer
0.20
4
Sarotti
0.50
5
Viver
0.50
6
T600
0.70
7
Putt River
0.80
8
Klein Tools IR10
1.30
9
FKM
2.10
10
Ames Instruments
2.10
11
Sunot
2.60
12
Mestic
3.20
13
ThermoPro
3.80
14
Milwaukee
3.90
15
Klein Tools IR5
4.60
Time to Take a Reading (seconds)
Lower is faster
Speed matters for back-to-back measurements, and it is the one category the expensive guns dominate outright. The Klein Tools IR10 settled in 0.2 seconds and the Fluke in 0.3, more than three times faster than the $8 Sunot at 2.46 seconds. The Surer was slowest at 3.44 seconds, over seventeen times the Klein Tools IR10.
Full results table
Rank
Product
Result
1
Klein Tools IR10
0.20
2
Fluke
0.30
3
Klein Tools IR5
0.60
4
Viver
0.70
5
Mestic
1.12
6
T600
1.17
7
Sarotti
1.17
8
FKM
1.17
9
Milwaukee
1.27
10
Ames Instruments
1.63
11
Putt River
1.79
12
Kaizen
1.89
13
ThermoPro
1.95
14
Sunot
2.46
15
Surer
3.44
Distance-to-Spot Ratio
Inches of standoff per inch of measured circle; higher is better
A 12:1 ratio means the gun reads a 1 in circle from 12 in away; move back and the cone widens like a flashlight beam. The $38 Viver's 50:1 optics let it read that same 1 in target from over four times the distance the $245 Fluke can, which is the Fluke's single biggest practical limitation. The Milwaukee is the tightest of all at 10:1.
Full results table
Rank
Product
Result
1
Viver
50
2
Surer
30
3
Putt River
30
4
Ames Instruments
20
5
Klein Tools IR10
20
6
Sunot
12
7
Sarotti
12
8
Kaizen
12
9
Mestic
12
10
Klein Tools IR5
12
11
Fluke
12
12
Milwaukee
10
The Verdict
The Fluke wins on consistency rather than on any single result. It posted the
lowest cumulative error of the group at 8.8°F across the five accuracy tests,
finished first on the glossy steel plate at 2.4°F, tied the Kaizen for first on
the polished aluminum wheel at 0.1°F, took third in the freezer at 2.6°F, and
was the second-fastest gun at 0.3 seconds — good enough for the best average
finish in the field at 2.5. Two things temper that: it costs $245, and its 12:1
distance-to-spot ratio is among the tightest here, so it has to be held close to
anything small. Its emissivity control is also just a low/high toggle rather
than a numeric setting.
The value pick is the T600 at $9. It tied for second overall with an average
finish of 5.3, posted the third-lowest cumulative error at 18.0°F, tied for
second on concrete at 0.2°F, took second on the 386°F plate at 1.5°F, and read
in 1.17 seconds. Its one genuine weakness is cold steel, where it was 11.3°F
out; strip that round away and it is close to the Putt River and the Fluke. It
has no adjustable emissivity, which matters less than the spec sheets suggest —
across the whole field, moving off the 0.95 default mostly made shiny-surface
readings worse, and only the Ames Instruments improved on it at all. The Viver
tied the T600 at 5.3 and is the pick if reach is what matters, with a 50:1 spot
ratio and a 0.1°F win on concrete, though its 22°F error on the hot plate is a
real caveat.
Price is a poor predictor here. The $63 Putt River took second on cumulative
error at 12.6°F and won the hot plate outright at 1.2°F, while the $65 Klein
Tools IR5 and the $104 Klein Tools IR10 landed 31.6°F and 33.3°F cumulative —
worse than the $19 Sarotti at 19.0°F. Two other findings are worth weighing
before buying. First, hot metal is where cheap sensors fail hardest: the Kaizen
missed by 24°F and the Viver by 22°F on the 386°F plate, and the Mestic would
not return a usable reading in the freezer at any emissivity setting, so neither
temperature extreme should be assumed. Second, display legibility in sunlight is
a real buying factor and was assessed subjectively: the Kaizen and the Fluke
earned the best possible rating of one and are genuinely clear outdoors, while
the dark screens on the FKM, the Mestic, the Viver, the Sarotti, the Putt River,
and the Ames Instruments range from very difficult to unreadable in direct sun.