# Foot-pounds to Joules (ft·lbf to J)

> Convert foot-pounds to joules: 1 ft·lbf = 1.35582 J. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

- Page id: `foot-pounds-to-joules` · Quantity: Energy (`energy`, base unit J) · Tool: `convert_units`
- Canonical page: https://tttkmbb.com/conversion/foot-pounds-to-joules · This document: https://tttkmbb.com/conversion/foot-pounds-to-joules.md · JSON: https://tttkmbb.com/conversion/foot-pounds-to-joules.json (add `?value=` for a result)

## Formula

- `1 ft·lbf = 1.35582 J`
- `joules = foot-pounds × 1.355817948`
- Reverse: `foot-pounds = joules × 0.7375621493`

The factor follows from the SI definitions of both units (NIST SP 811); values below are rounded to 6 significant figures, the API returns up to 12.

## Worked examples

- 5 ft·lbf = 6.77909 J
- 12.5 ft·lbf = 16.9477 J
- 100 ft·lbf = 135.582 J

## Conversion table

| Foot-pounds (ft·lbf) | Joules (J) |
| --- | --- |
| 1 | 1.35582 |
| 2 | 2.71164 |
| 3 | 4.06745 |
| 4 | 5.42327 |
| 5 | 6.77909 |
| 6 | 8.13491 |
| 7 | 9.49073 |
| 8 | 10.8465 |
| 9 | 12.2024 |
| 10 | 13.5582 |
| 15 | 20.3373 |
| 20 | 27.1164 |
| 25 | 33.8954 |
| 30 | 40.6745 |
| 40 | 54.2327 |
| 50 | 67.7909 |
| 75 | 101.686 |
| 100 | 135.582 |
| 200 | 271.164 |
| 250 | 338.954 |
| 500 | 677.909 |
| 1000 | 1355.82 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=ft_lbf&to_unit=J` → unified JSON envelope with `result.values.result`, `formula`, `factor`, `sources`, `freshness`
- MCP: server `https://tttkmbb.com/mcp`, tool `convert_units` with `{"value":5,"from_unit":"ft_lbf","to_unit":"J"}`
- All energy units: https://tttkmbb.com/api/v1/units?quantity=energy · full converter: [Energy Converter](https://tttkmbb.com/conversion/energy.md)
- Authentication: none. Freshness: `static` (fixed conversion factors).

## FAQ

**How many joules are in one foot-pound?**

1 ft·lbf = 1.35582 J. The factor comes from the SI definitions of both units (NIST SP 811 / BIPM), so it is exact or correct to at least 10 significant figures.

**What is the formula to convert foot-pounds to joules?**

Multiply the value in foot-pounds by 1.355817948: joules = foot-pounds × 1.355817948. For example, 5 ft·lbf = 6.77909 J.

**How do I convert joules back to foot-pounds?**

Multiply by the inverse factor 0.7375621493 (foot-pounds = joules × 0.7375621493), or use the joules-to-foot-pounds page.

## Related conversions

- [Joules to foot-pounds](https://tttkmbb.com/conversion/joules-to-foot-pounds.md) (reverse)
- [Kilocalories (food calories) to Kilojoules](https://tttkmbb.com/conversion/kcal-to-kj.md)
- [Kilojoules to Kilocalories (food calories)](https://tttkmbb.com/conversion/kj-to-kcal.md)
- [Joules to Calories (small, thermochemical)](https://tttkmbb.com/conversion/joules-to-calories.md)
- [Calories (small, thermochemical) to Joules](https://tttkmbb.com/conversion/calories-to-joules.md)
- [Kilowatt-hours to Megajoules](https://tttkmbb.com/conversion/kwh-to-mj.md)
- [Megajoules to Kilowatt-hours](https://tttkmbb.com/conversion/mj-to-kwh.md)
- [Kilowatt-hours to BTU](https://tttkmbb.com/conversion/kwh-to-btu.md)
- [BTU to Kilowatt-hours](https://tttkmbb.com/conversion/btu-to-kwh.md)

## Data Sources

- NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors — https://www.nist.gov/pml/special-publication-811 (standard, retrieved 2026-09-24)
- BIPM – The International System of Units (SI Brochure, 9th edition) — https://www.bipm.org/en/publications/si-brochure (standard, retrieved 2026-09-24)
- Wikipedia – Conversion of units — https://en.wikipedia.org/wiki/Conversion_of_units (reference, retrieved 2026-09-24)