A closed refrigerator keeps food safe for up to 4 hours after the power goes out. A full freezer holds its temperature for approximately 48 hours, and a half-full one for 24 hours. Those are the USDA's figures. The timer above counts from the moment you tell it the power went off.
What the timer is based on
Every number on this page comes from one document: the USDA Food Safety and Inspection Service guide "Keep Your Food Safe During Emergencies". We read it on 23 October 2026. The agency's website blocked our automatic checker, so we read it in a browser and copied each figure by hand.
The timer shows three things. How long the fridge has left, how long the freezer has left (full or half full, you choose), and the temperature to look for when the power returns: 40 °F or below in the fridge, 0 °F or below in the freezer. The USDA says to keep an appliance thermometer in both, so you can check the real temperature.
What to do while the clock runs
Keep the doors closed. That is the first instruction in the USDA's list and it matters more than anything else on it, since every opening lets warm air in.
If the outage lasts past 4 hours, the USDA says you can transfer food to a cooler and fill it with ice or frozen gel packs, then add ice as it melts so the food stays at 40 °F or below. Plan the cooler before you need it.
The freezer holds its cold better when it is full. The USDA suggests filling empty spaces with frozen plastic jugs of water, bags of ice or gel packs, and grouping food together in both appliances. Small, thin packages and anything in the door or at the front will defrost faster than large, thick items at the back.
Dry ice is an option for a long outage. According to the USDA, fifty pounds of dry ice should hold an 18-cubic-foot freezer for 2 days. Do not touch it with bare hands or let it rest against food.
When the power comes back
The USDA's rule is blunt: never taste food to determine its safety. If the fridge was without power for more than 4 hours, it lists what to discard, including meat, poultry, fish, eggs, milk, soft cheeses, cooked leftovers and cut fruit. The full list is on the USDA page linked below.
Frozen food that has thawed but still contains ice crystals is on the safe list, and so is food that stayed at 40 °F or below. Both may be refrozen, although quality may suffer. Opened mayonnaise, tartar sauce and horseradish are the odd ones out: the USDA says to discard them if they were held above 50 °F for over 8 hours.
Mistakes people make
The first is treating 4 hours as a target. It is a limit, and it assumes the door stayed shut.
The second is opening the door to check. Every look shortens the time.
The third is mixing up the two appliances. In our own offline AI test, one small model told us that a closed fridge keeps food cold for 48 hours. The library it was reading said 4, and 48 hours is the full-freezer figure. If you ask a chatbot about food safety, check the number against the source.
Last, not knowing when the power went out. The USDA does not say what to do here, so this part is our judgement: start the clock at the earliest time the outage could have begun.
For questions about meat, poultry and egg products, the USDA runs a toll-free hotline at 1-888-674-6854. It is open Monday through Friday, with recorded messages around the clock.