PickfolioFill a glass with ice, add water, stir, and hold the probe at least 2 inches deep without touching the glass. After at least 30 seconds it should read 32 °F. If it doesn't, adjust it the way your thermometer's instructions describe — or replace it if it can't be adjusted. The boiling-water check is less reliable at altitude, because water boils below 212 °F there.
Good fit if
- Your thermometer was dropped, is old, or gives readings you don't trust
- You're about to cook something where temperature is about safety, like poultry
- You want a routine check you can repeat before big cooking days
Not ideal if
- Infrared (surface) thermometers — they measure surfaces and are checked differently
- Oven or fridge thermometers — follow their makers' instructions
On this page
Why bother checking
A thermometer that reads a few degrees high can make undercooked food look done. USDA calls the process of checking accuracy calibration, and describes two home methods: ice water and boiling water 1. Ice water is the one USDA marks as best for most thermometers 1.
Method 1: ice water (start here)
- Fill a large glass with ice cubes, add drinking water, and stir well 1.
- Put the probe in at least 2 inches deep, without touching the sides or bottom of the glass 1.
- Wait at least 30 seconds, and read it without taking the probe out 1.
- It should read 32 °F 1. Texas A&M AgriLife Extension treats a reading within 2 degrees either way as accurate 2.
Use plenty of ice. A glass that is mostly water warms up and gives you a misleadingly high number.
Method 2: boiling water (with a catch)
Bring clean water to a boil, put the probe in at least 2 inches deep without touching the pot, and wait at least 30 seconds. At sea level it should read 212 °F 1.
The catch is altitude. USDA notes that at higher elevations water boils lower — at least 2 °F lower and perhaps as much as 5 °F lower — so a "wrong" reading may just be your location 1. If you live well above sea level, stick with ice water, or ask your local Cooperative Extension office for the boiling point where you live.
If it reads wrong
| What you have | What to do |
|---|---|
| Dial thermometer with a nut under the dial | Turn the calibration nut until it reads correctly — follow the maker's instructions 1 |
| Digital thermometer with a calibration function | Use the calibration steps in its manual |
| Thermometer with no way to adjust | USDA says you may need to replace it 1 |
| Reading drifts or jumps between checks | Replace the battery first, then check again |
Checklist: a quick accuracy routine
- Use a full glass of ice with a little water, stirred 1.
- Probe at least 2 inches deep, not touching the glass 1.
- Wait at least 30 seconds before reading 1.
- Expect 32 °F; within 2 degrees is considered accurate by Texas A&M AgriLife 2.
- Adjust using your thermometer's own instructions, or replace it if it can't be adjusted.
- Re-check after a drop, a battery change, or before a big cooking day.
- Clean it the way USDA advises: hot, soapy water or the maker's instructions — most thermometers shouldn't be submerged 1.
What this guide can't tell you
We can't tell you whether a particular brand holds its calibration over time; that would take long-term testing we haven't done. Your thermometer's manual is the final word on how to adjust it.
Sources
- USDA Food Safety and Inspection Service — Kitchen Thermometers. Checked Oct 21, 2026.
- Texas A&M AgriLife Extension — Calibrating Your Food Thermometer (PDF). Checked Oct 21, 2026.
How this page was made
Research-based guide, evidence level E1: Based on maker documentation, manuals and public guidance, each linked with the date we checked it. This is not a hands-on test. Research and drafting were AI-assisted, then every factual claim was matched to the sources above before publishing. No brand paid for or reviewed this page. How we research · Editorial policy