Work from one pound-force over one foot.
Foot-pounds to BTU Converter — ft-lb to BTU
Convert Foot-pound (ft-lb) to BTU (BTU) using the exact conversion factor (1 foot-pound = 0.0012850675 btu). See the formula, worked examples, conversion table, history, and common uses.
Foot-pounds to BTU converter
Converter
Engineering Converter
Convert common stress, force, torque, power, and energy units used in engineering.
Context values
Some unit families need one extra value for a physically accurate result.
British thermal unit.
Result = input x 1.355817948 / 1055.055853.
Energy units are compatible.
Reserved above the conversion cards and below the converter.
About Converting Foot-pounds to BTU
Foot-pound and BTU both measure a quantity used in structural or mechanical engineering — commonly stress, pressure, force, torque, power, or energy — where converting between the unit conventions used in different regions, industries, or equipment specifications is a routine part of design work. Specifically: Work from one pound-force over one foot, and british thermal unit.
Formula
btu = foot-pounds × 0.00128506746346
This factor comes from each unit's defined relationship to the category's base unit: 1 foot-pound equals 1.35581794833 base units, and 1 btu equals 1055.05585262 base units, so dividing one by the other gives the direct foot-pound-to-btu factor of 0.00128506746346.
Simple example
1 ft-lb × 0.001285067463 = 0.0012850675 BTU
1 foot-pound = 0.0012850675 btu.
Real-world example
100 ft-lb × 0.001285067463 = 0.1285067463 BTU
100 foot-pounds = 0.1285067463 btu.
Conversion table
| Foot-pound (ft-lb) | BTU (BTU) |
|---|---|
| 1 ft-lb | 0.0012850675 BTU |
| 10 ft-lb | 0.0128506746 BTU |
| 50 ft-lb | 0.0642533732 BTU |
| 100 ft-lb | 0.1285067463 BTU |
| 500 ft-lb | 0.6425337317 BTU |
| 1,000 ft-lb | 1.285067463 BTU |
Reverse conversion: BTU to Foot-pound
0.0012850675 BTU × 778.1692623 = 1.000000028 ft-lb
0.0012850675 btu = 1.000000028 foot-pounds.
foot-pounds = btu × 778.169262266
For a page dedicated to this direction, see BTU to Foot-pound.
Understanding the Foot-pound (ft-lb)
Work from one pound-force over one foot.
Understanding the BTU
BTU (BTU) measures energy. A British thermal unit is defined as exactly 1,055.05585262 joules (the International Table BTU). It is classified as a US customary unit.
Where it's used: United States (HVAC, heating, and appliance energy ratings)
Uses of the BTU today
- Air conditioner and furnace capacity ratings in the US
- Water heater and appliance energy specifications
- US energy industry (natural gas is often billed via BTU content)
History of the BTU
The BTU originated in 19th-century steam engineering as the heat needed to raise one pound of water by one degree Fahrenheit, paralleling the calorie's metric definition. Several slightly different BTU values existed historically before the 'International Table' BTU was standardized at exactly 1,055.05585262 joules.
Historical origin. BTU was not the invention of a single named person; it developed through the process described above.
BTU — sources
- NIST Special Publication 811 — Documents the International Table BTU's exact joule equivalence.
Reserved between the cards and the FAQ so the page stays balanced.
Frequently asked questions
How many btu are in 1 foot-pound?
1 foot-pound equals 0.0012850675 btu, using the exact defined conversion factor rather than an estimate.
How do I convert foot-pound to btu?
Multiply the foot-pound value by 0.001285067463. The converter above does this instantly to whatever precision you set.
How do I convert btu back to foot-pound?
Use the reverse factor: 1 btu equals 778.1692623 foot-pounds. You can also use the swap control in the converter above to flip the direction instantly.
What is a foot-pound?
Foot-pound (ft-lb) is a unit of engineering.
What is a btu?
BTU (BTU) measures energy. A British thermal unit is defined as exactly 1,055.05585262 joules (the International Table BTU). It is classified as a US customary unit.
Is the foot-pound to btu conversion exact?
Yes. A British thermal unit is defined as exactly 1,055.05585262 joules (the International Table BTU). That fixed definition is what the converter above uses, so any rounding you see is a display choice, not a limitation of the math.
Why do engineering unit conventions vary so much by region and industry?
Pressure, force, and stress can be expressed in metric (pascal, newton), US customary (psi, pound-force), or older and industry-specific units (atmosphere, torr, kip) depending on the country, industry, and even the equipment manufacturer, which is why engineers routinely need to convert between them when working across specs from different sources.