# Accuracy of no touch thermometers **URL:** \ **Category:** Factual Questions\ **Created:** [April 2, 2021, 1:23pm UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223 "2021-04-02T13:23:01Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![kayaker](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kayaker/32/441_2.png) [@kayaker](https://boards.straightdope.com/u/kayaker)\ **Post date:** [April 3, 2021, 3:32pm UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/21 "2021-04-03T15:32:47Z")
I was playing around with my MIL’s no touch thermometer, inserting the batteries, etc. I pointed it at her forehead. So, she asked if she had a temperature and I told her she did. She looked concerned, so I pointed out that _everything_ has a temperature and that she meant “fever”. We ended up discussing physics, Kelvin, atoms, etc for an hour. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [April 3, 2021, 6:24pm UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/22 "2021-04-03T18:24:17Z")
> [@carnivorousplant](#): > > > [@Richard\_Pearse](#): > > > > What use would an external body thermometer be if it wasn’t calibrated to approximate an internal reading? > > > > It measures your surface temperature and adjusts to give a corresponding body temperature. It doesn’t need to be super accurate, it just needs to be consistent and to discern between fever and not fever. > > An interesting point. > To answer an earlier question, the thermometer display tenths of a digit, but is only accurate within .4 degrees F. Yes, it has more precision than accuracy. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [April 3, 2021, 6:26pm UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/23 "2021-04-03T18:26:53Z")
> [@DPRK](#): > > If the thermometer displays some sort of “adjusted” temperature, not only would I expect it to say so in the instructions, it seems it should specify “point only at forehead” or something like that. That’s what mine says. It even specifies to point it at the right temple for the most accurate reading. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [April 5, 2021, 10:35am UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/24 "2021-04-05T10:35:41Z")
[quote=“Richard\_Pearse, post:16, topic:939223”] What use would an external body thermometer be if it wasn’t calibrated to approximate an internal reading?[/quote] We measure body temperature by several other methods (oral, rectal, axillary, ear). To my knowledge, none of those methods reports anything other than the actual temperature of that part of the body; correct interpretations of those measurements rely on an understanding of the range of normal values for temperatures measured _in those locations_. I’m not understanding why forehead temperature measurement should be treated any differently. ---
**Author:** ![Richard\_Pearse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/richard_pearse/32/13144_2.png) [@Richard\_Pearse](https://boards.straightdope.com/u/Richard_Pearse)\ **Post date:** [April 5, 2021, 10:54am UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/25 "2021-04-05T10:54:16Z")
I’ve just done a little research, temporal thermometers run about 1°F cooler than an oral thermometer. Implication being that there is no calibration happening, but you do have to point it at the right place, not just randomly at your forehead. Right temple is what mine says. > **[Types of Thermometers, Their Accuracy, and How to Use Them](https://www.healthline.com/health/types-of-thermometers#types)** > > There are many types of thermometers to choose from. The ages of your household members, as well as personal preference, can help you determine which one to buy. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [April 5, 2021, 1:26pm UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/26 "2021-04-05T13:26:53Z")
> [@Machine\_Elf](#): > > We measure body temperature by several other methods (oral, rectal, axillary, ear). To my knowledge, none of those methods reports anything other than the actual temperature of that part of the body; correct interpretations of those measurements rely on an understanding of the range of normal values for temperatures measured _in those locations_ . I’m not understanding why forehead temperature measurement should be treated any differently. > [@Richard\_Pearse](#): > > I’ve just done a little research, temporal thermometers run about 1°F cooler than an oral thermometer. Implication being that there is no calibration happening, but you do have to point it at the right place, not just randomly at your forehead. Right temple is what mine says. Something does not add up. I have a couple of IR thermometers. What I don’t have is a _calibrated_ IR thermometer; indeed, pointing them both at the same spot just now shows a 0.3 C difference, and there is an option to adjust things assuming you know the true temperature. However, on one of them, fiddling around with one of the settings switches the display between “Surface temp” and “Body temp”, with “Body temp” reading 2 C higher than “Surface temp” when pointed at my wrist. There is an instruction to aim the thing at the centre of the forehead when reading Body Temp. ---
**Author:** ![filmore](https://avatars.discourse-cdn.com/v4/letter/f/7993a0/32.png) [@filmore](https://boards.straightdope.com/u/filmore)\ **Post date:** [April 5, 2021, 1:51pm UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/27 "2021-04-05T13:51:58Z")
I have a no touch thermometer and it always seems to show the same forehead temperature of 97.1. I was worried it was just printing ‘97.1’ regardless of the actual temperature, but I can point it at different body parts and get different temperatures. Like my wrist might be 96 and my toes might be 92. I also took my temp using an oral thermometer and the temperature difference was consistent between the two. So I feel pretty confident that the thermometer is working well. One thing to note is that no touch thermometers are reading the _infrared_ light being emitted from the material. As you might imagine, different materials emit different amounts of infrared light even if they are at the same temperature. You can sometimes feel the difference with your hand. If you put your hand near (not touching) cast iron versus aluminum at the same temperature, the cast iron will feel much hotter since it is radiating much more infrared compared to the aluminum. When using a infrared thermometer in general, you’re supposed to change the emissivity setting depending on the material being tested so you get accurate results. Body thermometers are supposed to be calibrated for skin emissivity. Your forehead temperature may be affected if there is anything which might block radiant heat, such as lotions, sunscreen, sweat, etc. The most accurate temperature will be from a thermometer making direct contact with your body, but that isn’t practical for wide-scale testing. The no touch thermometers are generally accurate enough to indicate if there is a problem rather than giving a precise and accurate body temperature. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [April 5, 2021, 1:54pm UTC](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223/28 "2021-04-05T13:54:53Z")
> [@filmore](#): > > I was worried it was just printing ‘97.1’ regardless of the actual temperature, My right temple is up from 97.2 to 97.7 this morning. 🙂 [Previous page](https://boards.straightdope.com/t/accuracy-of-no-touch-thermometers/939223.md?page=1)