Microwave Defrost Time Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/9/2026
In a microwave, on the defrost setting, count about 12 minutes per kilogram of food (or 5 to 7 minutes per 500 g). A 500 g piece therefore takes about 6 minutes to thaw.
Explanation
A microwave's defrost setting runs at reduced power (often 20 to 30% of the appliance's maximum power), delivered in bursts, to give heat time to spread toward the center of the food without starting to cook the outside before the inside has thawed — a real risk if full power were used. This calculator uses a median benchmark of about 12 minutes per kilogram (or 5 to 7 minutes for 500 g of meat or poultry), a range regularly cited for this setting. This method remains noticeably faster than refrigerator thawing (see our thawing time calculator to compare safe methods), but comes with an important food-safety constraint: food thawed in the microwave already starts warming in places, pushing it into the temperature zone favorable to bacterial growth — it must therefore be cooked immediately after thawing, without delay, and never put back in the refrigerator for later use. Actual microwave power varies noticeably from one appliance to another (often between 700 and 1,200 W): this benchmark therefore remains an order of magnitude to adjust by checking and turning the pieces halfway through, never an exact guaranteed measurement for your specific appliance. For converting a temperature between oven types before cooking that same food once thawed, our oven temperature conversion calculator covers a related but distinct topic.
Example: 500 g of meat
Inputs
Food weight: 500 g (0.5 kg).
Calculation
Defrost time = 0.5 × 12 = 6 minutes.
Result
This 500 g piece takes about 6 minutes to thaw on the microwave defrost setting.
Frequently asked questions
Why does a microwave use reduced power to defrost?
Because at full power, the outside of the food would start cooking before heat had time to reach the still-frozen center, a mismatch that would give an uneven result (cooked edges, still-frozen core). The reduced power and intermittent delivery of the defrost setting let heat spread more evenly through the food before its surface gets too hot.
Should food be cooked immediately after microwave defrosting?
Yes, without delay: unlike refrigerator thawing, where the food stays continuously at a safe temperature, microwave defrosting already heats certain areas of the food beyond the safety limit, which encourages bacterial growth if cooking isn't immediate. Food thawed this way should never be put back in the refrigerator for later use.
Is this time the same for every microwave?
No, the actual power of domestic microwaves generally ranges between 700 and 1,200 W, which directly affects defrosting speed. This calculator gives a median order of magnitude to adjust by checking and turning the pieces halfway through, rather than a guaranteed duration for a specific appliance.