About the Microwave Wattage Converter
This microwave wattage converter adjusts cooking times printed on ready meals, popcorn bags and recipes to match your own microwave. Enter the time and wattage on the instructions plus the wattage of your oven, and it tells you how long to cook — in minutes and seconds — along with a chart for every common wattage from 600 W to 1250 W.
Microwave power is the rate at which energy is delivered to the food, so a weaker oven needs proportionally longer to deliver the same energy. Instructions written for a 1000 W oven take about 43% longer in a 700 W model, and a 1200 W oven finishes about 17% sooner. The calculator also shows the power level that would make a stronger oven behave like the one in the recipe.
Your wattage is usually printed on a label inside the door, on the back, or in the manual (it is the output power, not the input power). Results are a starting point: food shape, starting temperature and container all matter, so stir or rotate halfway, let food stand for a minute, and check that reheated leftovers reach 165°F (74°C).
With the default inputs, the cook for is 4m 17s. Change any value above to recalculate instantly.
How to use the microwave wattage converter
- 1Enter the cooking time from the package or recipe.
- 2Enter the wattage the instructions are written for (often 800 W, 1000 W or 1100 W).
- 3Enter your microwave’s output wattage from the label inside the door.
- 4Cook for the adjusted time, stirring or rotating halfway.
- 5Let the food stand, then check it is piping hot all the way through.
Formula and method
A microwave rated at P watts delivers P joules of energy per second to the food. To heat the same food by the same amount you need the same energy, so time × wattage stays constant: t₂ = t₁ × W₁ ÷ W₂. Halving the power doubles the time.
The power-level suggestion uses the same idea in reverse: running a stronger oven at W₁ ÷ W₂ of full power (most ovens cycle the magnetron on and off) delivers roughly the recipe’s wattage, so you can keep the printed time. Real ovens are not perfectly linear, so check food a little before the time is up.
- t₁
- Time on the instructions
- W₁
- Wattage the instructions were written for
- W₂
- Output wattage of your microwave
- t₂
- Adjusted time for your microwave
Worked examples
3 minutes at 1000 W in a 700 W microwave
180 seconds × 1000 ÷ 700 = 257 seconds, so cook for about 4 minutes 17 seconds — roughly 43% longer.
4 min 30 s at 800 W in a 1200 W microwave
270 seconds × 800 ÷ 1200 = 180 seconds. A 1200 W oven needs only 3 minutes, a third less time — or run it at about 67% power for the full 4:30.
Popcorn: 2 min 15 s at 1100 W in a 900 W oven
135 seconds × 1100 ÷ 900 = 165 seconds, or 2 minutes 45 seconds. With popcorn, stop when popping slows to 2 seconds between pops.
Frequently asked questions
How do I convert microwave time from 1000 W to 700 W?+
Multiply the time by 1000 ÷ 700, which is about 1.43. So 2 minutes at 1000 W becomes about 2 minutes 51 seconds at 700 W, and 5 minutes becomes about 7 minutes 9 seconds.
How do I find my microwave’s wattage?+
Look for a label inside the door frame, on the back or underneath the oven, or check the manual. Use the output power (often 700–1200 W), not the higher input power. Many models also print it on the rating plate as “Output: 1000 W” or similar.
Is a higher-wattage microwave better?+
Higher wattage cooks faster and more evenly for dense foods, but it is easier to overcook small portions. Lower-wattage compact models (600–800 W) need longer times and more stirring.
What power level equals a lower-wattage microwave?+
Divide the lower wattage by your wattage. To imitate an 800 W oven in a 1200 W microwave, use about 67% power (level 7) and keep the original time.
Why is my food still cold in the middle after converting?+
Microwaves heat the outer few centimetres; the centre warms by conduction. Stir, rotate or let food stand for a minute or two, and use a thermometer to check leftovers reach 165°F (74°C).