Convert foot-pound (force) to joule.

Convert foot-pound (force) (ft·lbf) to joule (J). This is a fixed-ratio conversion — multiply the input by the factor below.

Formula

J = ft·lbf × 1.35582

Reference values

Things to watch for

• The 'calorie' in nutrition labels is actually a kilocalorie (kcal, sometimes Cal with capital C). A '200 calorie' candy bar is 200 kcal = 836 kJ.
• 1 kWh = 3.6 MJ (exactly). Used for billing electricity.
• Electron-volts (eV) are convenient at atomic/molecular scales; joules at human scales; kWh at building scales.

What is a joule?

The joule is the SI unit of energy, defined as one newton-meter of work (1 J = 1 N·m). Physics, scientific energy calculations, and food labels in some countries.

How to convert ft-lbf to joule

To convert a value from ft-lbf (ft-lbf) to joule (J), apply the conversion factor shown in the formula above. The calculation is the same whether you do it by hand, in a spreadsheet, or with the live converter on this page.

Steps:

1. Take your input value in ft-lbf.
2. Apply the formula J = ft·lbf × 1.35582.
3. The result is your value in J.

For repeated calculations, save the formula in a spreadsheet or use the live converter at the top of this page — it handles the math automatically and displays the result as you type.

Frequently asked questions

How do I convert ft-lbf to J?

Apply the formula ft-lbf → J shown above, or just type your value into the converter at the top of this page. The result updates instantly.

Which is bigger, ft-lbf or J?

This depends on the conversion ratio in the formula. If the factor multiplied by your value gives a larger number, then J is the smaller unit (so it takes more of them to express the same quantity). If the result is smaller, then J is the larger unit.

When would I use ft-lbf versus J?

Both units measure energy, so the choice depends on context. Ft-lbf is typically used for food labeling, batteries, fuel, and electric utility billing; joule similarly. Most professional fields standardize on one or the other based on regional conventions or technical tradition.

How precise is this ft-lbf to J conversion?

The conversion factor shown is the internationally defined exact value (or the best-published approximation if the relationship is irrational, like degrees-to-radians). The live converter on this page uses double-precision floating-point math, accurate to about 15 significant digits — far beyond any practical engineering need.

Is the conversion ratio exact, or an approximation?

Most unit conversions between SI metric units, and between SI and US customary units, have been formally defined as exact values since the 1959 international yard-pound agreement and subsequent SI redefinitions. Exceptions are unit pairs that involve irrational numbers (radians, e.g.) or empirical conversions (like food calories, which depend on temperature). When in doubt, consult the formula at the top of this page.

Related conversions

See also