How long do leftovers actually last in the fridge?

The USDA guideline for most cooked leftovers is three to four days in the refrigerator, kept at or below 40 degrees Fahrenheit. After that, spoilage bacteria and, more dangerously, illness-causing bacteria can build to unsafe levels even when the food still looks and smells fine. Cooked rice and pasta sit at the shorter end because of a heat-resistant bacterium, Bacillus cereus, that survives cooking and produces toxins if the food cools slowly and lingers. Deli meats and prepared salads with mayo also want to be eaten promptly.

Freezing resets the clock: leftovers frozen within that safe window keep for months, losing quality but not safety, and the three-to-four-day rule applies again once thawed in the fridge. When reheating, bring leftovers to 165 degrees throughout, which kills active bacteria, though it does not always destroy toxins already produced, which is exactly why the original storage time matters more than the reheat. Label containers with the date, since day three of a mystery container is a bet nobody should make from memory.