Package directions may be tested in a microwave with a different output wattage from yours. Enter the stated wattage and time, then your microwave’s output wattage to get a proportional starting time.
Microwave wattage conversion calculator
Adjust a package or recipe time when its reference wattage differs from your microwave’s output wattage.
This is a starting estimate, not a food-safety guarantee. Follow the package or recipe method, stir or rotate as directed, allow standing time and verify safe internal temperature with a food thermometer.
Microwave time conversion formula
The estimate keeps nominal energy constant:
Adjusted time = listed time × listed wattage ÷ your microwave wattage
A lower-wattage microwave therefore receives a longer time; a higher-wattage microwave receives a shorter one. Read our microwave wattage guide if you are unsure which number to use.
Find your microwave’s output wattage
The USDA Food Safety and Inspection Service advises checking inside the door, the serial plate or the owner’s manual. Do not automatically use the larger electrical-input figure from the rating plate when the manual lists a separate cooking-output wattage.
Why the answer is a starting point
Microwave heating is uneven, and nominal wattage does not describe food shape, starting temperature, moisture, power cycling or an older oven’s real output. Follow any stirring, rotation, covering and standing-time directions. The USDA microwave-safety guidance recommends checking food in several places with a thermometer when a safe internal temperature matters.
Worked example
A package specifies 3 minutes at 1,000 W, but the available microwave is 800 W. The calculation is 180 seconds × 1,000 ÷ 800 = 225 seconds, or 3 minutes 45 seconds.
Frequently asked questions
Does “50% power” mean half the wattage?
Many conventional microwaves cycle the magnetron on and off to average a lower power level. Do not use this converter to replace a recipe’s specific power-level and stirring instructions.
Can the calculator prove food is safely cooked?
No. Time conversion cannot verify internal temperature. Use the package method and a food thermometer for meat, poultry, fish, eggs and leftovers.