Find Your Microwave's Wattage By Using It To Boil Water

Find Your Microwave's Wattage by Using It to Boil Water

Your microwave can be just as good at cooking as your stove, but it takes getting familiar with your power settings. You have to adjust it according to what you're cooking, and that means knowing your wattage. If you're not sure what your microwave's wattage is, boil a cup of water to find out. Photo by alangraham999.

If your microwave's wattage isn't on the machine or you just can't seem to find it, Epicurious offers this quick tip to get an estimate:

To find an approximation of your machine's wattage, fill a microwave-safe liquid measuring cup with 1 cup cold water. Microwave on High and keep an eye on it, noting how long it takes for the water to come to a boil…

  • 1 1/2 minutes: 1,200 watts
  • 2 minutes: 1,000 watts
  • 2 1/2 minutes: 800 watts
  • 3 minutes: 700 watts
  • 4 minutes: 600 watts

Once you figure it out, you can adjust your power settings to make sure your food is cooked properly. Epicurious offers suggestions for that, too, so check out their full post at the link below.

The Simple Trick to Cooking Food Perfectly in the Microwave [Epicurious]


    Or you could have a look at the Microwave, it's usually marked on it somewhere, at the very least it should be on a label on the back of the unit

    Mine has 1200w clearly on the front

      Yes but older microwaves become less powerful over time. So this procedure may still be useful if you have an older one

    Be VERY careful with the water after you do it. Can get much hotter than normal boiled water.

      yeah best to have something to break the water surface while microwaving it, one would think the super heating would affect the results of this test.

    It is almost a moot point unless there is agreement on what the "power" rating of a microwave actually means. Is it the power delivered to the food? If so, then to cause a specific change in the temperature of the water, requires a precise amount of power defined by the formula for the specific heat of water, which is:

    Watts = Change in temperature (degC) * Mass of water * 4181 / Time (seconds) to heat

    To actually boil the water requires additional consideration of the energy input required to change the phase of the water from liquid to gas.

    On the other hand there are various standards that measure the power of a microwave, including JIS and IEC. These Standards have changed over a time so, for example, with one new edition of the test method, a previously "700W" microwave suddenly became a "750W" one.

    When I see "times based on 1000W microwave oven" in a recipe I have no idea what they are talking about since the power rating test method is not defined. Different recipe books are likely to base the power rating on different methodologies. So I just use trial and error...

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