Adjust a microwave recipe or package time for your microwave's output wattage. Enter the original time and reference wattage, then your microwave wattage to get an immediate browser-only estimate.
Editorial author: Starlight Tools Editorial TeamReviewed and updated: 29 July 2026
Cooking time and wattage
Use 0–360 minutes and 0–59 seconds. The total time must be at least 1 second.
W
The wattage used by the instructions.
W
Use output/cooking watts, not electrical input.
Converted time
Estimated cooking time2 min 51 secSet the timer to approximately 02:51
Time multiplier1.43×
Time difference51 sec longer
Power change1000 W → 700 W
5-second setting2 min 50 sec
A 700 W microwave is lower-powered, so the nominally equivalent time is longer. Use this as the point to begin checking and add short intervals only if needed.
Microwave safety: converted time is only a starting estimate
Microwaves can heat unevenly and leave cold spots. Follow the recipe, package, and appliance instructions first. Cover and vent food as directed, stir or rotate midway when appropriate, and keep the full stated standing time.
For meat, poultry, eggs, fish, casseroles, and leftovers, use a clean food thermometer in several places after the standing time. USDA guidance says reheated leftovers should reach 165°F (74°C). Do not use this calculator to shorten a manufacturer-required standing time or to replace safe internal-temperature checks.
Microwave wattage conversion formula
Converted time = original time × recipe watts ÷ your microwave watts
The formula holds nominal microwave output energy constant. If a 1000 W recipe calls for 2 minutes and your microwave is 700 W:
This is an energy-equivalence estimate, not a complete heating model. Microwave field pattern, food geometry, mass, moisture, starting temperature, container, cycling behavior, and inverter design can all change real cooking time.
Assumption: use the same power-level setting specified by the recipe in both microwaves—usually High/100%. Do not treat rated wattage and the microwave's numbered power level as interchangeable.
Quick microwave wattage conversion chart
Five minutes at the recipe wattage converted to a different microwave
Recipe wattage
Your microwave
Original time
Converted time
Adjustment
1000 W
700 W
5:00
7:09
2:09 longer
1000 W
800 W
5:00
6:15
1:15 longer
1000 W
900 W
5:00
5:33
0:33 longer
1000 W
1100 W
5:00
4:33
0:27 shorter
1000 W
1200 W
5:00
4:10
0:50 shorter
700 W
1000 W
5:00
3:30
1:30 shorter
Times are rounded to the nearest second. Actual food heating is not perfectly linear, so begin checking at the converted time rather than assuming the food is done.
How to convert microwave cooking time
Enter the stated time. Use the minutes and seconds from the recipe or package.
Enter the recipe wattage. Look for wording such as “based on a 1000 W microwave.”
Find your output wattage. Check inside the door, the rating plate, or the owner's manual. Avoid using the larger electrical input figure.
Convert the time. The tool multiplies the original time by the ratio of recipe watts to your microwave watts.
Check, stir, and stand. Follow every package step, begin checking at the estimate, add short intervals if needed, and observe the original standing time.
Worked examples
1000 W recipe to 700 W
2:00 × 1000 ÷ 700 = 2:51. The lower-powered microwave needs about 51 seconds more.
800 W recipe to 1200 W
4:30 × 800 ÷ 1200 = 3:00. The higher-powered microwave needs about 1 minute 30 seconds less.
1100 W recipe to 900 W
1:45 × 1100 ÷ 900 = 2:08. The lower-powered microwave needs about 23 seconds more.
Methodology, limits, and sources
The calculator uses the nominal relationship between power, time, and energy: energy equals power multiplied by time. Keeping nominal energy constant gives the displayed wattage-ratio formula. Results are calculated from total seconds and rounded to the nearest second; the optional 5-second setting is separately rounded to the nearest 5 seconds for microwaves with coarser timer controls.
GE Appliances notes that recipes developed for one microwave wattage can generally be adapted for another by increasing or decreasing time, and recommends starting with the lowest stated time and checking doneness. USDA FSIS explains that higher-wattage microwaves cook faster, advises checking the oven's door label, serial plate, or manual for wattage, and stresses even heating, stirring or turning, standing time, and food-temperature checks.
Privacy: the calculator runs entirely in your browser. It does not transmit, save, or track the time and wattages you enter.
Microwave wattage conversion FAQs
How do I convert microwave cooking time for a different wattage?
Multiply the recipe time by the recipe wattage, then divide by your microwave's output wattage. For example, 2 minutes at 1000 W becomes about 2 minutes 51 seconds at 700 W.
Does a lower-wattage microwave need more time?
Yes. Under the nominal energy-equivalence model, lower wattage needs more time; higher wattage needs less time.
Where can I find my microwave wattage?
Check the label inside the door, the serial or rating plate, or the owner's manual. Use the output cooking wattage, not the appliance's electrical input or power-consumption figure.
Is the converted time exact?
No. It is a starting estimate. Food shape, mass, moisture, starting temperature, container, microwave design, power cycling, and standing time all affect the result. Check at the estimate and add short intervals if needed.
Should I change the microwave power level too?
Use the power level stated by the recipe or package. This calculator assumes the same power-level setting in both microwaves, usually High/100%. Reduced-power behavior varies between cycling and inverter models.
Can I use this for frozen meals and packaged food?
Use package directions first. A converted time can help when the package provides a reference wattage, but follow all stirring, rotation, venting, standing-time, and temperature instructions.
Does standing time change when wattage changes?
Do not scale or skip the recipe's standing time. It is part of the cooking process, especially for dense foods, and should be followed as written unless the manufacturer says otherwise.
Are my inputs private?
Yes. The calculation runs locally in your browser and the tool does not send or store the entered time or wattages.
