Refrigerator Temperature Checker

A refrigerator should be 40°F (4°C) or below, and a freezer 0°F (-18°C)

The FDA says to keep the refrigerator at 40°F or below and the freezer at 0°F. This checker adds one limit on the cold side: a fridge reading below 32°F (0°C) is flagged as too cold, because produce, tofu and drinks can start to freeze. So the safe range it uses is 32°F to 40°F for the fridge and 0°F or below for the freezer.

Those numbers apply to the actual air temperature where your food sits, measured with a thermometer, and not to the number on a dial or display. Enter a reading for each compartment above and you get a verdict for each. If a power outage or breakdown pushed the temperature up, add how many hours it stayed over the limit and the checker sorts what to throw away from what you can keep.

When it is worth checking with a thermometer

A refrigerator that is running too warm looks and sounds normal. You often find out only after food has already spoiled. These are good moments to measure.

• Food goes bad sooner than it used to: if milk or leftovers turn before their dates, the fridge may be running above 40°F.
• Hot weather or a door that is opened constantly: warm kitchen air and frequent openings push the inside temperature up.
• A new fridge or a move: it takes time to settle after you plug it in, and the spot it sits in affects the real temperature.
• After you change the setting: measure again in the same place later to see whether the new setting actually took effect.
• After an outage, a breakdown or a door left ajar: you need both the current temperature and the time it was too warm to decide what to move or toss.

The FDA recommends an appliance thermometer for exactly this: "Buy one for the fridge, one for the freezer, and check them often." Its guidance is to confirm the temperature is consistently 40°F or below in the fridge and 0°F or below in the freezer.

How to use the checker and take a reading

1. Place a thermometer: put a freestanding appliance thermometer in the middle of the compartment, among the food, and close the door. Avoid the spot directly in front of the cold air vent and the door shelves.
2. Wait, then read: after several hours, open the door and read it right away. Standing with the door open lets the temperature climb.
3. Enter the value: type each reading into the fridge or freezer on the screen above. One compartment is enough, and the buttons under each box fill in common values. If your thermometer reads in Celsius, pick °C at the top first.
4. Add the hours (optional): after an outage or breakdown, enter how long the temperature stayed above the limit. If you do not know exactly, enter how long the outage lasted and the checker will lean toward the safer verdict.
5. Read the result: each compartment gets a level, and the thermometer drawing shows where the reading falls against the limits. Read "What to do now" together with the food table.

If you measured in more than one spot, enter the highest reading. The warmest spot is the one that tells you whether everything in the compartment is safe.

The levels this checker uses

The fridge and freezer have different limits, so each has its own levels. A value exactly on a limit counts as safe, so 40°F is safe and 40.1°F is too warm. A reading in Celsius is converted to Fahrenheit and rounded to one decimal place before it is judged.

Time counts too. If the fridge stays above 40°F, or the freezer above 40°F, for more than 2 hours, the verdict becomes unsafe and the checker tells you to throw out the perishable foods. If it is unsafe and you do not know how long, it advises throwing food out. At 2 hours or less it advises moving the food to another fridge or a cooler. Exactly 2 hours does not count as more than 2 hours. The 2-hour rule and the 40°F line come from the foodsafety.gov power outage chart, which sorts food held at 40°F (4°C) or above for more than 2 hours.

Example readings and what they mean

The same temperature leads to different advice depending on the compartment and the hours. This table applies the checker's own rules.

What the FDA says, and how other countries compare

The FDA says it is important to keep the refrigerator at 40°F or below and the freezer at 0°F. Its page says to use an appliance thermometer to be sure the temperature is consistently 40°F or below in the fridge and 0°F or below in the freezer. The checker uses exactly those two numbers as its safe limits.

Home recommendations in other countries differ slightly, which is why the same fridge can look fine in one country's guidance and borderline in another's. Conversions below are rounded.

Japan's ministry adds that most bacteria grow slowly at 10°C and stop growing at -15°C, but they are not killed, so food should be used up sooner rather than later. Freezing pauses bacteria and does not remove them, which is worth remembering when you clear out old food from the freezer.

Common reasons a fridge runs warm

If the checker says too warm, look for a cause before only turning the control down. A colder setting will not hold if cold air cannot circulate or the door does not seal. Check these first.

• The door is opened often or left open for a long time.
• The door does not close fully because of a worn seal or something caught in it.
• Hot food was put in without cooling first.
• Thick frost has built up in the freezer.
• The unit is crowded so cold air cannot move around the food.

If the temperature keeps rising after you adjust the setting, call a repair service.

After an outage, look at the hours too

foodsafety.gov says a refrigerator will keep food safe for up to 4 hours during a power outage if the door stays closed. A full freezer holds a safe temperature for approximately 48 hours, or 24 hours if it is half full and the door remains closed. The FDA adds that during an outage you should keep the fridge and freezer doors closed as much as possible, and it suggests freezing water in sealable bags ahead of time to help keep things cold.

When the power returns, check the thermometers before using any food, then enter the hours above the limit. The foodsafety.gov chart sorts refrigerated food held at 40°F (4°C) or above for more than 2 hours. Raw and leftover cooked meat, poultry, fish, milk, eggs, cooked pasta and rice, and cut fruit and vegetables are thrown away. Hard cheeses, butter, uncut fruit and vegetables and bread can stay. Soy sauce, Worcestershire, barbecue and hoisin sauces are on the keep list, while fish sauce and oyster sauce are on the throw-away list. The full fridge and freezer tables are in "What to keep or toss after an outage" on the screen above.

Frozen food that still has ice crystals, or that is at 40°F or below, can be refrozen, though quality may suffer. Ice cream and frozen yogurt are the exception and go in the trash once they have melted. The FDA's rule for the unknown case is simple: if you are unsure how long the food was at or above 40°F, throw it out. Never taste food to decide whether it is safe.

Common mistakes

• Trusting the display or dial: the checker needs a thermometer reading from where the food sits.
• Measuring with the door open: the temperature climbs while the door is open and you read a higher value than the real one.
• Re-measuring right after a change: the inside needs time to follow a new setting.
• Setting the fridge below freezing: colder is not better, and produce, tofu and drinks can freeze.
• Opening the door during an outage to check: every opening lets cold air out and shortens how long the food stays safe.
• Judging by smell or taste: a normal smell does not mean the food is safe, so go by temperature and time.

Limits of this checker

• It reads one temperature and one time you enter. It does not know a food's use-by date or tell you whether a food is already spoiled.
• The 2-hour rule, the food tables and the refreezing line (40°F) come from U.S. government material (FDA and foodsafety.gov). One boundary differs between them: the FDA fridge target is “40°F or below,” while the outage chart counts food “at 40°F or above.” The checker treats exactly 40°F as safe, so if food sat at 40°F through an outage, treat it as over the limit.
• It does not diagnose why a refrigerator is warm. If the temperature stays high after you change the setting, contact a repair service.
• Foods not on the foodsafety.gov chart are not judged. For anything that spoils easily, when in doubt, throw it out.

As of October 19, 2026. The FDA page (current as of March 5, 2024) and the foodsafety.gov chart (last reviewed August 8, 2024) were checked on that date.

Sources

• 01U.S. FDA. Refrigerator Thermometers – Cold Facts about Food Safety (current as of March 5, 2024)Fridge 40°F or below, freezer 0°F; appliance thermometers; keep doors closed during an outage; unsure how long, throw it out
• 02FoodSafety.gov. Food Safety During Power Outage (last reviewed August 8, 2024)4 hours, 48 hours and 24 hours; food tables for 40°F (4°C) or above for more than 2 hours; refreezing conditions
• 03UK Food Standards Agency. How to chill, freeze and defrost food safely (December 18, 2017)Fridge between 0 and 5°C, freezer around -18°C
• 04AESAN (Spain). Familias: comidas en el centro escolarPerishable food refrigerated, if possible below 4°C
• 05AESAN (Spain). ¿Congelas y descongelas de forma segura? (November 4, 2021)Constant -18°C or below
• 06Japan Ministry of Health, Labour and Welfare. Six points for preventing food poisoning at home (Japanese)Fridge 10°C or below, freezer -15°C or below; bacteria slow but are not killed
• 07Korea Ministry of Food and Drug Safety. Food poisoning prevention notice (July 7, 2022, Korean)Home storage: fridge 5°C or below, freezer -18°C or below

Frequently asked questions

Tools to use with this one