Convert Foot-pounds to British Thermal Units
Foot-pound (ft·lb) to British Thermal Unit (BTU) unit conversion — enter any value below to get an instant result, or use the table for common values.
Results from this calculator are estimates provided for general informational purposes only, based on formulas, rates, and standards commonly accepted as of 2026. Figures may differ slightly from other calculators or professional sources due to rounding methods, differing assumptions, or regional regulations, and rules may change over time. Always consult a qualified professional — such as a financial advisor, healthcare provider, or other relevant specialist — before making decisions based on these results.
Result
1 ft·lb = 0.0012850675 BTU
1 Foot-pound = 0.0012850675 British Thermal Units
1 British Thermal Unit = 778.16926 Foot-pounds
1 ft·lb in every supported unit
Conversion chart: Foot-pound to British Thermal Units
Conversion table
| Foot-pound (ft·lb) | British Thermal Unit (BTU) |
|---|---|
| 0.01 ft·lb | 1.28507E-05 BTU |
| 0.1 ft·lb | 0.00012850675 BTU |
| 1 ft·lb | 0.0012850675 BTU |
| 2 ft·lb | 0.0025701349 BTU |
| 3 ft·lb | 0.0038552024 BTU |
| 5 ft·lb | 0.0064253373 BTU |
| 10 ft·lb | 0.012850675 BTU |
| 20 ft·lb | 0.025701349 BTU |
| 50 ft·lb | 0.064253373 BTU |
| 100 ft·lb | 0.12850675 BTU |
| 1000 ft·lb | 1.2850675 BTU |
Foot-pound (ft·lb)
Definition: The energy transferred when a force of one pound-force acts through a distance of one foot, equal to about 1.356 joules.
History: A natural byproduct of the imperial system's foot-and-pound base units, it became the standard energy and work unit in English and American engineering and mechanics well before the metric system was adopted for scientific use.
Current use: Used today mainly to express torque and mechanical work in US engineering contexts, such as the tightening specification for bolts or the energy rating of a swinging hammer or falling weight.
British Thermal Unit (BTU)
Definition: The energy required to raise the temperature of one pound of water by one degree Fahrenheit, standardized at exactly 1,055.05585262 joules in its "International Table" definition.
History: Originating in 19th-century British engineering and steam-power practice, the BTU became the standard energy unit in English-speaking industry before metrication, tied to the imperial pound-and-Fahrenheit measurement system rather than the metric kilogram-and-Celsius system used for the calorie.
Current use: Still the standard rating unit for air conditioners, furnaces, and water heaters in the United States, where an appliance's heating or cooling capacity is quoted in BTUs per hour.
Supported Units
| Unit | Symbol | In Joules |
|---|---|---|
| Joule | J | 1 J |
| Kilojoule | kJ | 1000 J |
| Calorie | cal | 4.184 J |
| Kilocalorie | kcal | 4184 J |
| Watt-hour | Wh | 3600 J |
| Kilowatt-hour | kWh | 3600000 J |
| British Thermal Unit | BTU | 1055.0559 J |
| Foot-pound | ft·lb | 1.3558179 J |
| Electronvolt | eV | 1.60218E-19 J |
| Erg | erg | 1E-07 J |
About These Parameters
- Value
- The amount of energy you want to convert, expressed in the "From" unit. Accepts decimals — enter a food label's Calorie count, an electricity bill's kWh reading, or any other energy figure.
- From Unit
- The unit your input value is currently measured in — for example, kilocalorie if you're starting from a nutrition label, or kilowatt-hour if you're starting from a power bill.
- To Unit
- The unit you want the result converted into. Use the swap button to flip From and To instantly.
How Energy Conversion Works
The Formula
Every unit here is defined by a fixed multiplier relative to the joule. To convert a value from one unit to another:
result = value × (factor of "From" unit ÷ factor of "To" unit)
For Foot-pound → British Thermal Unit: multiply by 0.0012850675. For example, 1 ft·lb × 0.0012850675 = 0.0012850675 BTU.
Why "Calorie" vs. "calorie" Causes Confusion
The small calorie (cal) is the energy needed to raise one gram of water by one degree Celsius — but the "Calorie" printed on a US nutrition label is actually a kilocalorie (kcal), exactly 1,000 times larger. The convention of capitalizing "Calorie" to mean kilocalorie dates back to 19th-century nutrition science and has stuck ever since, so a food listed as "200 Calories" really contains 200,000 small calories. A typical 2,000 kcal daily diet is equal to 8,368 kilojoules — the figure printed on nutrition labels in most countries outside the US.
From Electronvolts to Kilowatt-hours: The Scale of Energy
Because every unit here reduces to the joule, this converter spans an enormous range of physical scales on a single page — from the electronvolt (about 1.6 x 10⁻¹⁹ J, the energy of a single accelerated electron, used in particle physics) up to the kilowatt-hour (3.6 million J, the energy a typical US household uses in roughly an hour of running several appliances at once, and the unit electricity bills are calculated in). An average American home uses on the order of 28-30 kWh per day, which works out to over 100 billion billion electronvolts — a useful reminder of just how small atomic-scale energies really are.
Example
1 ft·lb equals 0.0012850675 BTU. For scale, that's about 0× a typical 2,000 kcal daily diet (2,000 kcal, or 6171920.1 ft·lb).
Frequently Asked Questions
How many British Thermal Units are in 1 Foot-pound?
1 Foot-pound (ft·lb) equals exactly 0.0012850675 British Thermal Units (BTU).
Why is a food Calorie 1,000 times a scientific calorie?
Early nutrition scientists in the late 1800s, including Wilbur Atwater, found the small calorie produced awkwardly large numbers when describing food energy, so they adopted the kilocalorie instead and capitalized it as "Calorie" to distinguish it in writing. The capitalization convention was widely lost in casual use, which is why "200 Calories" on a label actually means 200,000 of the small scientific calories (cal).
How many kWh does an average home use?
A typical US household uses roughly 28-30 kilowatt-hours per day, or around 850-900 kWh per month, though this varies significantly with climate, home size, and appliance efficiency — electric heating, air conditioning, and water heaters are usually the largest contributors.
How accurate are these conversions?
Every conversion factor used here is the exact, internationally defined value (e.g. 1 calorie = exactly 4.184 joules, 1 BTU = exactly 1,055.05585262 joules) — results are limited only by floating-point display precision, not by rounded conversion constants.