Microwave instructions often assume a cooking power different from your appliance. Matching power multiplied by time estimates how long the same food needs at another output wattage. Use the cooking output rating from the manual, which can be lower than the electrical input rating on the back.
How to use
- Enter the microwave wattage used by the original instructions.
- Enter the original cooking duration and your microwave cooking output wattage.
- Check the converted duration, stir as directed, and retain the original standing time.
How the calculation works
New time = original time × original cooking output watts ÷ your cooking output watts. This approximates P₁t₁ = P₂t₂.
Example
A 3-minute instruction at 1,000 W converts to approximately 4 minutes 17 seconds at 700 W. The lower-powered oven takes about 43% longer in this simplified model.
Factors affecting the result
- Microwave output is not the same as wall-plug electricity consumption.
- Food shape, moisture, container geometry and cold spots limit the accuracy of energy matching.
- Reduced power settings may cycle full power on and off instead of delivering constant lower power.
Frequently asked questions
Where do I find my microwave wattage?
Look for cooking power or output power in the manufacturer manual or product specification. Do not substitute a larger input-power number.
Does the converted time include standing time?
No. Standing time serves a separate purpose: heat continues to spread through the food. Keep the standing period required by your recipe or package.
Why is my food still cold in the middle?
Equal calculated energy does not ensure even heating. Stir or rearrange food as instructed and check temperature in more than one location when food safety is involved.
Sources & methodology
Calculation basis: Physics-based approximation. Methodology
- Cooking Safely in the Microwave Oven — USDA Food Safety and Inspection Service
- Measuring electricity — U.S. Energy Information Administration
Last updated: September 15, 2026