Enter the length, width, and height of a room into the calculator to determine the estimated wattage needed to heat the room.

Watt Heat Formula

The following formula is used to estimate the wattage (power) needed to heat a room.

W = L*W*H * 1.25
  • Where W is the wattage required to heat a room (Watts)
  • L is the length of the room (ft)
  • W is the width of the room (ft)
  • H is the heigh of the room (ft)

This formula is a simple estimation, and the true power required to heat a room depends drastically on the insulation properties of the room.

Watt Heat Definition

A watt of heat is the standard unit of measure of heat transfer and is defined as one joule of energy per second of time.

Example Problem

How to calculate watt heat?

  1. First, determine the length of the room.

    In this example, the room is measured to have a length of 20ft.

  2. Next, determine the width of the room.

    The width of the room is measured to be 10ft.

  3. Next, determine the height of the room.

    The room has a standard height of 8ft.

  4. Finally, calculate the watt heat.

    Using the formula above, the watts required to heat the room are estimated to be:
    W = L*W*H * 1.25
    W = 20*10*8 * 1.25
    W = 2000 watts.