Garage Heat Lab

Watts to BTU Converter

Formula: BTU/hr = watts × 3.412. Type a number to convert it, and see how much garage it would heat.

BTU/hr

5,118BTU/hr

As a heater, this delivers enough for about 120 sq ft of garage at average insulation on a 40°F rise. Check it in the garage heater calculator.

Convert the other way: BTU to watts →

Updated

Watts to BTU/hr chart

WattsBTU/hrGarage it can heat
100 W341.2 BTU/hrUnder 50 sq ft
500 W1,706 BTU/hrUnder 50 sq ft
750 W2,559 BTU/hr60 sq ft
1,000 W3,412 BTU/hr80 sq ft
1,500 W5,118 BTU/hr120 sq ft
2,000 W6,824 BTU/hr160 sq ft
3,000 W10,236 BTU/hr240 sq ft
4,000 W13,648 BTU/hr320 sq ft
5,000 W17,060 BTU/hr400 sq ft
7,500 W25,590 BTU/hr600 sq ft
10,000 W34,120 BTU/hr800 sq ft
Garage area assumes average insulation, an 8 ft ceiling and a 40°F rise. Estimate only.

What this conversion means for a heater

Watts and BTU per hour both measure power, the rate of heat. An electric heater turns all of its power into heat, so its wattage converts directly: a 1,500 W plug-in heater makes about 5,118 BTU/hr, whatever the label says.

Ready to size a real heater? The garage heater calculator includes your climate and insulation.

Questions people ask

How many BTU is 1,500 watts?

About 5,118 BTU/hr. That is the output of a standard plug-in space heater.

How many BTU is 7,500 watts?

About 25,590 BTU/hr, enough for a typical two-car garage at average insulation on a 40°F rise.

How do I convert watts to BTU?

Multiply watts by 3.412. For example, 5,000 W × 3.412 = 17,060 BTU/hr.

Are BTU and BTU/hr the same?

Not exactly. BTU is an amount of energy and BTU/hr is a rate. Heater labels usually say BTU when they mean BTU/hr.

Sources

Sources last checked October 31, 2026.

  1. EIA: British thermal units (accessed October 2026)