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Baby & child.

Updated: 20 May 2022

How we test digital thermometers

Discover the lengths we go when testing digital thermometers to unearth the Best Buys that give the most accurate readings and are simple to use
Patrick Gallagher
Digital ear thermometer being used

We only recommend digital thermometers that deliver accurate temperature readings, have easy to use functions and are comfortable to use. 

We put every simple digital thermometer through the same set of rigorous tests to find out which one is best. Our tests include practical assessments carried out by our ease-of-use specialists and technical measurements to ensure that each of our thermometer reviews answers all the key questions you might have, including:

  • Is this digital thermometer accurate?
  • Is it simple to use?
  • How comfortable is it to use?
  • How fast is it at taking temperature readings?
  • Should I buy it?

Find out which models are accurate and simple to use in our digital thermometer reviews.

What are Which? Best Buys and Don’t Buys?

Best Buy digital thermometers pass our tough accuracy tests and also impressed in our various ease of use and comfort assessments. A Best Buy comes with a solid overall recommendation, although you should still read our reviews to check for any weaknesses that might impact your buying decision.

Meanwhile, digital thermometers that fail our temperature accuracy tests are made Don’t Buys, regardless of how easy or pleasant they are to use.

  • Best Buy digital thermometers tick the most important boxes – they quickly provide accurate temperature readings, have an easy-to-read display and are simple to use.
  • Don't Buy digital thermometers provide temperature measurements that can't be trusted and you should avoid using them.

Is this digital thermometer accurate?

In order to test whether a digital thermometer will guarantee you consistently accurate results, we use criteria based on an international standard.

We take readings using each of the digital thermometers on test and compare them with a platinum resistance thermometer with calibration traceable to a national standard of temperature.

The accuracy measurements are performed with a thermostat-controlled circulating water bath that has settable temperatures and a stability of 0.01°C. All measurements are performed in an air-conditioned lab which is stabilised at an ambient temperature of 22°C.

We test across 11 temperature measuring points in order to get a complete idea of how accurate each thermometer is.

We don't produce a percentage test score when testing thermometers - they're either a pass or fail. However, for them to be a Best Buy, the thermometer also needs to achieve high scores for ease of use, the time it takes to get a temperature reading, comfort in use and the consistency of the readings.


Is it simple to use?

We use a mix of lab experts and a user panel made up of members of the public to work out how simple each digital thermometer is to use.

They comment on how easy it is to take temperature measurements, how clearly the numbers show up on the display, how simple it is to navigate through any additional features and functions, and how clear and complete the instruction manual is.

How comfortable is it to use?

Taking a temperature reading from a poorly child can be tricky if they're not feeling cooperative, and using a thermometer that feels uncomfortable certainly won't help.

To help you find the thermometers that feel best, our panel of triallists rate how comfortable each model is to use. Scores take into account self use and use on a child.

How fast is it at taking temperature readings?

We rate each digital thermometer on the time it takes to take a reading. This is based on the length of time in seconds each model takes to generate a stable temperature recording. The overall result is based on times taken for each of the 11 different test temperatures we measure.

Should I buy it?

All of the digital thermometers that pass our temperature accuracy tests can be relied on to give you a correct temperature reading when you need one. We give our Best Buy recommendation to products that both pass this test and achieve high scores for ease of use, comfort, convenience, and consistency.

Any thermometer that fails our accuracy test is named a Don't Buy – we think these are the digital thermometers you should avoid.