IR Thermometer is a non-contact style measuring tool with certain distance to get surface temperature by receiving all items' infrared. Basically this may let you know the accuracy would be larger then contact style, especially while they are still some distance existing between measured target and thermometer.

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Why the product always 2°C or 2% higher in accuracy than reading data? Because of above issues, the world leading manufacture of Infrared Thermometer, Raytek (now is owned by Fluke) found that each item possess different emissivity which affects temperature reading. Lucky, most of items would be near 0.95. Most items’ emissivity is between 0.93 and 0.97, which means there would be some accuracy issues involved. Thus they follow the optics and statistics theories creating 2 °C accuracy.

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Since Raytek is the leader in this industry, everybody followed their rules as guideline. When you check all IR thermometers in the market, you will find this accuracy is almost a principle for whole industry.

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Accuracy is stated as "+/-1%,1°C" (the typical accuracy translation is +/-1% or reading; +/-1°C). With 1% accuracy, at 100°C, allowable error would be +/-2°C (3.6°F); at 250°C allowable error is +/-3.5°C (6.3°F)