To calculate the space a heater requires, the heater has to be measured with a tape measure. This gives the square footage of the appliance and an idea of where the heater can fit in a room. There also needs to be space around the heater to prevent a fire.
First, measure the heater from one side to the other, with the tape measure running parallel to the floor at the heater's widest point. Then, measure it from top to bottom. Finally, measure from front to back, and multiply all three numbers. This provides the dimensions of the heater itself. No combustible material should be within 36 inches of the heater, so factor this distance in as well.