Which Type of Thermometer Is the Most Accurate?

Medically Reviewed on 8/24/2021
which type of thermometer is the most accurate
Digital thermometers give the most accurate body temperature readings. Learn about 4 different types of medical thermometers

Checking your temperature with a reliable medical thermometer can be very helpful in managing illness at home. And nowadays, most thermometers give accurate results within a few seconds. So how do you choose the right one for you and your family?

Digital thermometers give the most accurate body temperature readings. But the best thermometer is one that can be used easily and correctly. It is also helpful if your thermometer comes from a reliable manufacturer. Rectal thermometers are still considered by many doctors to be the most accurate for babies and children, but oral and forehead thermometers are also reliable and more convenient to use.

How do temperature readings vary?

Based on how a thermometer is administered, readings can vary:

  • Rectal temperature readings are about 0.5 to 1 degrees F higher than oral temperature readings.
  • Armpit (axillary) temperature readings are usually 0.5 to 1 degrees F lower than oral temperature readings. 
  • Ear (tympanic) temperature readings are about 0.5 to 1 degrees F higher than oral temperature readings.
  • Forehead (temporal) scanner readings are around 0.5 to 1 degrees F lower than oral temperature readings.

4 different types of medical thermometers

A typical thermometer is made up of two primary components: sensor and numerical reading. These make the temperature measurement visible in numerical value, which can be shown in Celsius or Fahrenheit. 

Below are 4 different types of medical thermometers and how they’re used.

1. Digital thermometers

Digital thermometers are more advanced types of thermometers, and when used correctly, provide the most accurate results. They are also easy to use, cost-friendly, and are widely available. 

These thermometers typically operate using heat sensors, which help measure the temperature of the human body. An electronic circuit and a display screen are used to display temperature readings. They are widely used to record readings from under the armpit and tongue or the rectum.

2. Clinical thermometers

Clinical thermometers, also called medical thermometers, are particularly designed for clinical purposes and used to measure the temperature of the human body. They are made of a long narrow glass tube that contains a bulb with mercury at its end. Currently, mercury thermometers are replacing digital thermometers due to environmental and safety concerns and require sterilization before use. 

The average temperature of the human body is 98.6 degrees F, although this range can vary between 95 to 107.6 degrees F. Clinical thermometers are designed to measure this typical temperature range.

3. Electronic ear thermometers

Electronic ear thermometers use infrared technology to measure the body temperature from inside the ear canal. They are also called tympanic thermometers because they measure temperature using the tympanic membrane with infrared energy given off by the heat source. These thermometers capture body temperatures quickly and are best suited for children. 

4. Forehead thermometers

Forehead thermometers capture the superficial temporal artery's temperature (a sub branch of the carotid artery) using infrared sensors. These thermometers have become quite popular because of their non-contact mechanism and are often used to measure people's temperatures in airports, stations, stores, and stadiums. 

While convenient because they do not require physical contact, forehead thermometers are not accurate because the temperature readings usually run about 1 degree F lower than digital thermometers.


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Medically Reviewed on 8/24/2021
Kemp C, ed. Temporal Artery Thermometers May Rival Rectal Thermometers in ED. AAP News. April 2013; 34 (4):2. https://aappublications.org/content/34/4/2.1

Mayo Clinic. Thermometer Basics: Taking Your Child's Temperature. https://mayoclinic.org/healthy-lifestyle/infant-and-toddler-health/in-depth/thermometer/art-20047410

Mogensen CB, Wittenhoff L, Fruerhøj G, Hansen S. Forehead or Ear Temperature Measurement Cannot Replace Rectal Measurements, Except for Screening Purposes. BMC Pediatr. Published 2018 Jan 26. doi:10.1186/s12887-018-0994-1

U.S. Food and Drug Administration. Non-contact Infrared Thermometers. https://www.fda.gov/medical-devices/general-hospital-devices-and-supplies/non-contact-infrared-thermometers

Non-Contact Thermometers for Detecting Fever: A Review of Clinical Effectiveness [Internet]. Ottawa (ON): Canadian Agency for Drugs and Technologies in Health. 2014 Nov 20. https://ncbi.nlm.nih.gov/books/NBK263237/