Enter the voltage and current into the calculator to determine the running watts; this calculator can also evaluate any of the variables given the others are known.

Running Watts Formula

The following formula is used to calculate the running watts for an electrical device:

 RW = V * I


  • RW is the running watts
  • V is the voltage
  • I is the current

To calculate the running watts, multiply the voltage by the current.

What is a Running Watts?

Running watts, also known as continuous watts, refer to the amount of power a device or appliance needs to function under normal operation. This is the standard measure of a generator’s capacity to deliver power. Running watts are calculated by multiplying the voltage by the current (in amperes) that a device uses when it is running normally. For example, if a device operates at 120 volts and uses 10 amperes, it would require 1200 running watts. It’s important to note that some devices may require more power to start up (known as starting watts or peak watts) than they do to continue running, so it’s crucial to consider both running and starting watts when determining the power needs for a device or a set of devices.

How to Calculate Running Watts?

The following steps outline how to calculate the Running Watts.

  1. First, determine the voltage (V) of the appliance.
  2. Next, determine the current (I) drawn by the appliance.
  3. Next, use the formula P = V * I to calculate the power (P) in watts.
  4. Finally, calculate the Running Watts by multiplying the power (P) by the power factor (PF).
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

voltage (V) = 120

current (I) = 5

power factor (PF) = 0.9