Microwave Wattage Converter

Check the label inside the door or on the back of the microwave. If no label is visible, use the boil test: microwave 1 cup (237 mL) of cold tap water and time how long it takes to boil. 1.5 minutes = ~1,000W, 2 minutes = ~800W, 2.5 minutes = ~650W, 3 minutes = ~500W. Most countertop microwaves sold today are 900-1,200W.

Microwave cooking time is inversely proportional to wattage. A recipe developed in a 1,000W microwave takes 43% longer in a 700W microwave (1,000/700 = 1.43x). Most published microwave recipes assume 1,000W. Always adjust time when your microwave differs from the recipe's assumed wattage.

Yes - reducing power level instead of increasing time gives the same result. If a recipe calls for 1,000W and your microwave is 700W, you could either cook 43% longer at full power, or cook for the original time at about 143% power (not possible) - so time adjustment is the correct method. However, for foods that benefit from gentler, slower heating, cooking at 70% power for longer in a 1,000W microwave is better than increasing time.