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Microwave Wattage Conversion Calculator

Convert microwave cooking times between wattages: if the package says 3 minutes at 1100 W, find the time for your 700, 800 or 1000 W oven, plus the power level that mimics a weaker microwave.

Wattage in the instructions

Your microwave wattage

Time in the instructions — minutes

Time in the instructions — seconds

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How it works

your time = package time × package watts ÷ your watts · power level to mimic a weaker oven = package watts ÷ your watts × 100%

A microwave heats food with a fixed output power, so the energy delivered is power × time. To deliver the same energy in a weaker oven you cook proportionally longer, and in a stronger one proportionally shorter — the rule used on frozen-food packaging that lists times for several wattages. Real heating is not perfectly linear (dense food, cold spots and turntable size matter), so start with the calculated time, stir or turn halfway, let the food stand and check that leftovers and meat reach 74 °C (165 °F) in the centre, as USDA advises.

Worked example

Instructions say 3:00 at 1100 W and your oven is 800 W: 3 × 1100 ÷ 800 = 4.125 minutes, about 4:08 — 37.5% longer. With a 1250 W oven it would be 3 × 1100 ÷ 1250 = 2:38.

Sources: USDA FSIS — Microwave Ovens and Food Safety

Frequently asked questions

How do I convert microwave times to a different wattage?

Multiply the time by the package wattage and divide by your oven's wattage. Going from 1100 W to 700 W multiplies the time by 1.57; from 700 W to 1000 W by 0.7.

How do I find my microwave's wattage?

Look at the label inside the door, on the back or in the manual — use the output (cooking) power, not the larger input power. Or time how long 1 cup (250 mL) of cold water takes to boil: about 2 minutes at 1000 W, 3 at 800 W, 4 at 600 W.

Can I use a lower power level instead?

Yes: on a 1100 W oven, power level 6–7 (about 60–70%) behaves roughly like a 700–800 W oven, so you can follow the package time for that wattage.

Is the conversion exact?

It is a good starting point. Always stir, rotate and let food stand 1–2 minutes, and check that it is steaming hot all the way through.

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This calculator is for educational purposes. Double-check important results before acting on them.