Convert Foot-pounds to Kilojoules
Foot-pound (ft·lb) to Kilojoule (kJ) 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 = 0.0013558179 kJ
1 Foot-pound = 0.0013558179 Kilojoules
1 Kilojoule = 737.56215 Foot-pounds
1 ft·lb in every supported unit
Conversion chart: Foot-pound to Kilojoules
Conversion table
| Foot-pound (ft·lb) | Kilojoule (kJ) |
|---|---|
| 0.01 ft·lb | 1.35582E-05 kJ |
| 0.1 ft·lb | 0.00013558179 kJ |
| 1 ft·lb | 0.0013558179 kJ |
| 2 ft·lb | 0.0027116359 kJ |
| 3 ft·lb | 0.0040674538 kJ |
| 5 ft·lb | 0.0067790897 kJ |
| 10 ft·lb | 0.013558179 kJ |
| 20 ft·lb | 0.027116359 kJ |
| 50 ft·lb | 0.067790897 kJ |
| 100 ft·lb | 0.13558179 kJ |
| 1000 ft·lb | 1.3558179 kJ |
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.
Kilojoule (kJ)
Definition: One thousand joules (10³ J), a convenient scale for everyday amounts of energy such as food intake or the work done by a household appliance.
History: A straightforward decimal multiple of the joule, it entered common use as the metric system spread through science and industry in the 19th and 20th centuries, growing more visible to the public once nutrition labeling required it.
Current use: The standard energy unit on nutrition labels in most of the world outside the United States, where food energy is expressed in kilojoules alongside or instead of kilocalories.
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 → Kilojoule: multiply by 0.0013558179. For example, 1 ft·lb × 0.0013558179 = 0.0013558179 kJ.
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 0.0013558179 kJ. 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 Kilojoules are in 1 Foot-pound?
1 Foot-pound (ft·lb) equals exactly 0.0013558179 Kilojoules (kJ).
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.