When you purchase a stove, you may find the heat output measured in watts, kilowatts or in British Thermal Units (BTUs). Most of the time the measurement will be given in the number of kilowatts per hour. To convert to BTU output, you need to first make sure you are talking about the same amount of time when you compare measurements. If you know any other measurement of energy output you can convert it to BTU output.
Things You'll Need
 Stove manual or manufacturer's information
 Calculator (if desired)

Determine the energy output of the stove from the label on the back of the unit or from the manufacturer's information. The listing should be in watts for electric stoves and will already be listed in BTUs for gas stoves. Most electric stoves have three sizes of heating elements: a small element using around 1,200 watts, a large element using 2,500 watts or two medium elements using 1,500 to 1,800 watts.

Total the watts for the four heating elements. For example, if you have one heating element of 2,500 watts, two heating elements of 1,500 watts and one heating element of 1,200 watts, your total wattage is 6,700 watts.

Divide by 1,000 to get the total kilowatts of output. In our example, 6,700 divided by 1,000 is 6.7.

Multiply by 3,412.12 to get the total BTUs per hour. In our example, 6.7 times 3,412.12 is 22,861.2 BTUs.
References
 Photo Credit gas stove image by Christopher Walker from Fotolia.com