British Thermal Units to Watt Hours
An instant British thermal units-to-watt hours converter, with the formula and a reference table below.
| British Thermal Units | Watt Hours |
|---|---|
| 1 BTU | 0.293071 Wh |
| 2 BTU | 0.586142 Wh |
| 3 BTU | 0.879213 Wh |
| 5 BTU | 1.465355 Wh |
| 10 BTU | 2.930711 Wh |
| 25 BTU | 7.326777 Wh |
| 50 BTU | 14.653554 Wh |
| 100 BTU | 29.307107 Wh |
How to use
- Enter a value in the British Thermal Units field.
- The Watt Hours figure appears immediately — no button to press.
- Typing in the Watt Hours field converts back to British Thermal Units the same way.
- Use the reference table for the values that come up most often.
British Thermal Units to Watt Hours formula
The factor from British thermal units to watt hours is 0.29307107.
Wh = BTU × 0.29307107
Why this factor: the British thermal unit and the watt-hour are both defined against the joule, so dividing one definition by the other gives 0.29307107 directly. Both definitions are set out in full below.
To go the other way, divide by 0.29307107 — or use the Watt Hours to British Thermal Units converter, which is the same calculation reversed.
Worked example
Start with 100 BTU. Multiply by 0.29307107 to get 29.307107 Wh.
100 BTU × 0.29307107 = 29.307107 Wh
The converter above does this for any value you type, in either direction.
What is a British thermal unit?
A BTU is the energy needed to raise one pound of water by one degree Fahrenheit.
Definition: The international-table BTU is about 1,055.056 joules.
Where it is used: US heating and air-conditioning capacity ratings, natural gas pricing, and boiler output.
Worth knowing: Air-conditioner ratings quoted as 'BTU' are really BTU per hour — a rate of cooling, not a quantity of energy.
What is a watt-hour?
A watt-hour is the energy delivered by one watt of power sustained for one hour.
Definition: Exactly 3,600 joules.
Where it is used: Battery capacity for laptops, e-bikes and power tools, and small-scale energy metering.
Worth knowing: Airline lithium-battery limits are set in watt-hours, which is why laptop and power-bank capacities are labelled in Wh.
British Thermal Units vs Watt Hours
The British thermal unit is a US customary unit while the watt-hour is a specialized unit. That is why the factor between them is not a round number: the two systems were defined independently and only later tied together by exact agreement.
Frequently asked questions
How many watt hours are in a British thermal unit?
One British thermal unit equals 0.29307107 watt hours.
What is the formula to convert British thermal units to watt hours?
Multiply the number of British thermal units by 0.29307107. To reverse it, divide by 0.29307107 instead.
How do I convert watt hours back to British thermal units?
Divide by 0.29307107, which is the same as multiplying by 3.41214163.
How many watt hours are in 10 British thermal units?
10 BTU works out to 2.930711 Wh.
Is there anything to watch out for with British thermal units?
Air-conditioner ratings quoted as 'BTU' are really BTU per hour — a rate of cooling, not a quantity of energy.
How is the British thermal unit defined?
The international-table BTU is about 1,055.056 joules.