Check the microwave’s label on the back, side, or inside the door frame
Look for “Output Power,” “Cooking Power,” or “Wattage”
Read the owner’s manual
Search the model number online
Check the manufacturer’s website
Use the wattage listed on the product sticker or serial plate
If only voltage and amperage are listed, multiply volts by amps to estimate input watts
Use a microwave wattage test with a known heating time and a standard test method
Compare cooking times with a microwave wattage chart
Use a watt meter to measure power draw
Note that input watts and output watts may be different