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

Formula

1 kcal = 4.184 kJ

kilojoules = kilocalories (food calories) × 4.184 — reverse: kilocalories (food calories) = kilojoules × 0.2390057361

The factor is derived from the SI definitions of both units (base unit: J) as listed in NIST SP 811; results on this page are shown 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

Kilocalories (food calories) to kilojoules conversion table

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) (reverse)
• Energy Converter — all energy units in one tool
• Joules to Calories (small, thermochemical)
• Calories (small, thermochemical) to Joules
• Kilowatt-hours to Megajoules
• Megajoules to Kilowatt-hours
• Kilowatt-hours to BTU
• BTU to Kilowatt-hours
• BTU to Joules
• Joules to BTU

Machine access

• API: GET https://tttkmbb.com/api/v1/convert?value=5&from_unit=kcal&to_unit=kJ
• MCP: server https://tttkmbb.com/mcp, tool convert_units with {"value":5,"from_unit":"kcal","to_unit":"kJ"}
• Markdown: https://tttkmbb.com/conversion/kcal-to-kj.md · JSON: https://tttkmbb.com/conversion/kcal-to-kj.json (add ?value= for a result) · Units: /api/v1/units?quantity=energy
• OpenAPI operationId: convert_units. Freshness: static. Authentication: none.

Sources

• NIST Special Publication 811 – Guide for the Use of the International System of Units (SI), Appendix B conversion factors (standard)
• BIPM – The International System of Units (SI Brochure, 9th edition) (standard)
• Wikipedia – Conversion of units (reference)