How Do You Calculate Microwave Wattage?

In order to calculate the wattage of a microwave, heat 1 liter, or approximately 1 quart, of room temperature water in the microwave for two minutes and three seconds. Then, multiply the difference in the temperatures before and after microwaving the water by 19.4 to find the wattage.

  1. Test the water

    Fill a microwave-safe container with 1 liter of water at room temperature (approximately 70 degrees Fahrenheit), and measure the exact temperature of the water.

  2. Heat the water

    Place the container in the microwave, set the timer for two minutes and three seconds, and press start. If the microwave does not have a timer, use a stopwatch.

  3. Calculate the microwave wattage

    Measure the temperature of the water after heating it. Calculate the difference in the water temperature before and after heating, and multiply this number by 19.4 to find the microwave wattage. This method generates results that are between 50 and 75 watts of the actual microwave wattage.