Foot Pounds to British Thermal Units
Type a value in either box to convert between foot pounds and British thermal units. The factor is 0.00128507.
| Foot Pounds | British Thermal Units |
|---|---|
| 1 ft·lb | 0.001285 BTU |
| 2 ft·lb | 0.00257 BTU |
| 3 ft·lb | 0.003855 BTU |
| 5 ft·lb | 0.006425 BTU |
| 10 ft·lb | 0.012851 BTU |
| 25 ft·lb | 0.032127 BTU |
| 50 ft·lb | 0.064253 BTU |
| 100 ft·lb | 0.128507 BTU |
How to use
- Enter a value in the Foot Pounds field.
- The British Thermal Units figure appears immediately — no button to press.
- Typing in the British Thermal Units field converts back to Foot Pounds the same way.
- Use the reference table for the values that come up most often.
Foot Pounds to British Thermal Units formula
To convert foot pounds to British thermal units, multiply by 0.00128506746.
BTU = ft·lb × 0.00128506746
Why this factor: the foot-pound and the British thermal unit are both defined against the joule, so dividing one definition by the other gives 0.00128506746 directly. Both definitions are set out in full below.
To go the other way, divide by 0.00128506746 — or use the British Thermal Units to Foot Pounds converter, which is the same calculation reversed.
Worked example
Given 2000 ft·lb, multiplying by 0.00128506746 yields 2.570135 BTU.
2000 ft·lb × 0.00128506746 = 2.570135 BTU
The converter above does this for any value you type, in either direction.
What is a foot-pound?
A foot-pound is the work done by one pound-force acting through one foot.
Definition: About 1.3558179 joules.
Where it is used: US mechanical work and torque figures, fastener specifications, and firearm muzzle energy.
Worth knowing: As a torque unit it is properly 'pound-foot' (lbf·ft); as an energy unit it is 'foot-pound'. The numbers coincide but the quantities differ.
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.
Foot Pounds vs British Thermal Units
The foot-pound and the British thermal unit belong to the same family of units, so converting between them is usually a matter of shifting a decimal point or applying a small whole-number factor.
Frequently asked questions
How many British thermal units are in a foot-pound?
One foot-pound equals 0.00128506746 British thermal units.
What is the formula to convert foot pounds to British thermal units?
Multiply the number of foot pounds by 0.00128506746. To reverse it, divide by 0.00128506746 instead.
How do I convert British thermal units back to foot pounds?
Divide by 0.00128506746, which is the same as multiplying by 778.169262.
How many British thermal units are in 10 foot pounds?
10 ft·lb works out to 0.012851 BTU.
Is there anything to watch out for with foot pounds?
As a torque unit it is properly 'pound-foot' (lbf·ft); as an energy unit it is 'foot-pound'. The numbers coincide but the quantities differ.
How is the foot-pound defined?
About 1.3558179 joules.