# Kilocalories (food calories) to Kilojoules (kcal to kJ)

> Convert kilocalories (food calories) to kilojoules: 1 kcal = 4.184 kJ. Exact conversion factor, formula, 22-row table and worked examples, with JSON API and MCP access.

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

## Formula

- `1 kcal = 4.184 kJ`
- `kilojoules = kilocalories (food calories) × 4.184`
- Reverse: `kilocalories (food calories) = kilojoules × 0.2390057361`

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 kcal = 20.92 kJ
- 12.5 kcal = 52.3 kJ
- 100 kcal = 418.4 kJ

## Conversion table

| Kilocalories (food calories) (kcal) | Kilojoules (kJ) |
| --- | --- |
| 1 | 4.184 |
| 2 | 8.368 |
| 3 | 12.552 |
| 4 | 16.736 |
| 5 | 20.92 |
| 6 | 25.104 |
| 7 | 29.288 |
| 8 | 33.472 |
| 9 | 37.656 |
| 10 | 41.84 |
| 15 | 62.76 |
| 20 | 83.68 |
| 25 | 104.6 |
| 30 | 125.52 |
| 40 | 167.36 |
| 50 | 209.2 |
| 75 | 313.8 |
| 100 | 418.4 |
| 200 | 836.8 |
| 250 | 1046 |
| 500 | 2092 |
| 1000 | 4184 |

## API

- `GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=kcal&to_unit=kJ` → 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":"kcal","to_unit":"kJ"}`
- 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 kilojoules are in one kilocalorie?**

1 kcal = 4.184 kJ. 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 kilocalories (food calories) to kilojoules?**

Multiply the value in kilocalories (food calories) by 4.184: kilojoules = kilocalories (food calories) × 4.184. For example, 5 kcal = 20.92 kJ.

**How do I convert kilojoules back to kilocalories (food calories)?**

Multiply by the inverse factor 0.2390057361 (kilocalories (food calories) = kilojoules × 0.2390057361), or use the kilojoules-to-kilocalories (food calories) page.

## Related conversions

- [Kilojoules to kilocalories (food calories)](https://tttkmbb.com/conversion/kj-to-kcal.md) (reverse)
- [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)
- [BTU to Joules](https://tttkmbb.com/conversion/btu-to-joules.md)
- [Joules to BTU](https://tttkmbb.com/conversion/joules-to-btu.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)