Watt Calculator

Wondering, “What size generator do I need?” With this wattage calculator, you will find the perfect generator size! It’s your tool for choosing the right power solution for your home, worksite, or leisure activities.


1. List Your Appliances: Enter all the appliances and devices you will be running with your generator into the “APPLIANCE” field. You can use the drop-down menu, which lists different categories with the most common devices. If you have several identical devices, enter the number into the “QUANTITY” field. If there is only one, just enter 1.

If your device is not in the drop-down menu, just click on “ADD CUSTOM APPLIANCE” and type the device’s name into the field.

To add more appliances or devices, click the “ADD APPLIANCE” button.

If you’ve made a mistake, you can delete the device by clicking the “REMOVE” button.

2. Find Wattage: Check the labels on your appliances or their manuals to find the running watts (continuous power) and starting watts (initial surge of power to start the appliance). If you can’t find it, look up the average wattage for common items online.

If you don’t know the starting watts and running watts of your device just click on the “PREFILL” button. The typical starting and running watts for the selected device will be prefilled.

All wattages are estimates. Your actual wattage of the devices may vary.

3. Enter Wattage: Enter the running watts and starting watts for each appliance into the calculator.

4. Calculate Total: In the output you get two numbers. The Total Running Watts and the Minimal Required Generator Power. The Total Running Watts is the combined continuous power use of all the devices you plan to run at the same time with a generator. The output Minimal Required Generator Power adds the running watts and the highest starting wattage to give you the total. This is the minimum wattage your generator needs to handle.

Please note: If you are powering a family home or a worksite, remember that multiple people might use the same circuit and start two devices at once, which will increase the starting watts needed.

5. Select a Generator: Use the total to pick a generator that can provide at least that amount of power. You can find many reviews of generators with various power capacities under the reviews section.

By following these steps, you can make sure you choose a generator that meets your power needs for both running and starting your appliances.

Printing Function: You can print the list of devices you’ve created using the “PRINT TABLE” button. If it doesn’t work, try using a different web browser.