Convert Kilocalories to Kilojoules – Energy Converter
This converter transforms energy values expressed in kilocalories (kcal) to kilojoules (kJ) using the internationally recognized thermochemical relationship so you can compare nutrition labels, laboratory results, and engineering data in SI units.
The tool follows SI-consistent practice: 1 kilocalorie (kcal) = 4.184 kilojoules (kJ). Guidance and references from national metrology and standards organizations are provided below for auditing, calibration, and interoperability.
Governance
Record 058e0f087909 • Reviewed by Fidamen Standards Committee
Interactive Converter
Convert between kilocalorie and kilojoule with precision rounding.
Quick reference table
| Kilocalorie | Kilojoule |
|---|---|
| 1 kcal | 0.24 kJ |
| 5 kcal | 1.2 kJ |
| 10 kcal | 2.39 kJ |
| 25 kcal | 5.98 kJ |
| 50 kcal | 11.95 kJ |
| 100 kcal | 23.9 kJ |
Methodology
We apply the fixed thermochemical conversion factor defined in international metrology guidance: multiply kilocalories by 4.184 to obtain kilojoules. This factor originates from measured definitions of the calorie and is the value used for nutrition labeling and most scientific work.
Where multiple historical calorie definitions exist, we adopt the thermochemical calorie (1 cal = 4.184 J) to remain consistent with SI practice and major standards bodies. For traceability and regulatory contexts consult the cited authoritative sources.
Worked examples
1 kcal → 4.184 kJ
100 kcal → 418.4 kJ
250 kcal → 1046.0 kJ
500 kcal → 2092.0 kJ
F.A.Q.
What is the exact relationship between kcal and kJ?
The accepted thermochemical relationship is 1 kilocalorie (kcal) = 4.184 kilojoules (kJ). This is the SI-consistent value used for scientific, nutritional, and regulatory reporting.
Why do some sources show a slightly different factor (e.g., 4.1868)?
Multiple historical definitions of the calorie exist (mean calorie, 15 °C calorie, thermochemical calorie). For consistency with SI and national metrology institutes we use the thermochemical definition (1 cal = 4.184 J). Use alternate factors only if a specific historical definition is required and document which definition was used.
How many significant digits should I report?
Match the precision to your input data and instrument uncertainty. For nutrition labels, one decimal place for kJ (or integer kJ) is common. For laboratory measurements, round according to your measurement uncertainty and traceability to standards (see NIST and BIPM guidance).
Does this converter handle negative values or zero?
Yes. The mathematical relationship is linear and applies to zero and negative values in contexts where negative energy is meaningful (e.g., bookkeeping of energy flows). Ensure negative results are physically meaningful for your application.
Is this suitable for regulatory nutrition labeling?
This conversion provides the standard numeric transformation used in nutrition labeling. Always follow the specific regulatory agency rules for rounding and presentation (for example, the relevant national food authority) when preparing labels or official documentation.
How do I ensure accuracy and traceability?
Use calibrated measurement equipment, document instrument uncertainty, and reference a recognized standard (NIST/BIPM/ISO). For critical work preserve raw data, calculation records, and the chosen definition of the calorie.
Sources & citations
- NIST — The International System of Units (SI) and unit conversion guidance — https://www.nist.gov/pml/weights-and-measures
- BIPM — International Bureau of Weights and Measures, SI Units — https://www.bipm.org/en/publications/si-brochure
- FDA — Food Labeling & Nutrition (guidance on energy declaration and rounding) — https://www.fda.gov/food/food-labeling-nutrition
- ISO 80000-1 — Quantities and units (international standard on units of measurement) — https://www.iso.org/standard/30669.html
- MIT OpenCourseWare — Thermodynamics and energy units (educational reference) — https://ocw.mit.edu
- NIST SP 811 — Guide for the Use of the International System of Units — https://www.nist.gov/pml/special-publication-811
Further resources
Related tools
External guidance
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
Record ID: 058e0f087909What changed (latest)
v1.0.0 • 2025-11-26 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Versioning & Change Control
Audit record (versions, QA runs, reviewer sign-off, and evidence).
What changed (latest)
v1.0.0 • 2025-11-26 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Public QA status
PASS — golden 25 + edge 120
Last run: 2026-01-23 • Run: golden-edge-2026-01-23
Engine
v1.0.0
Data
Baseline (no external datasets)
Content
v1.0.0
UI
v1.0.0
Governance
Last updated: Nov 26, 2025
Reviewed by: Fidamen Standards Committee (Review board)
Credentials: Internal QA
Risk level: low
Reviewer profile (entity)
Fidamen Standards Committee
Review board
Internal QA
Entity ID: https://fidamen.com/reviewers/fidamen-standards-committee#person
Semantic versioning
- MAJOR: Calculation outputs can change for the same inputs (formula, rounding policy, assumptions).
- MINOR: New features or fields that do not change existing outputs for the same inputs.
- PATCH: Bug fixes, copy edits, or accessibility changes that do not change intended outputs except for previously incorrect cases.
Review protocol
- Verify formulas and unit definitions against primary standards or datasets.
- Run golden-case regression suite and edge-case suite.
- Record reviewer sign-off with credentials and scope.
- Document assumptions, limitations, and jurisdiction applicability.
Assumptions & limitations
- Uses exact unit definitions from the Fidamen conversion library.
- Internal calculations use double precision; display rounding follows the unit's configured decimal places.
- Not a substitute for calibrated instruments in regulated contexts.
- Jurisdiction-specific rules may require official guidance.
Change log
v1.0.0 • 2025-11-26 • MINOR
Initial publication and governance baseline.
Why: Published with reviewed formulas, unit definitions, and UX controls.
Areas: engine, content, ui • Reviewer: Fidamen Standards Committee • Entry ID: 18d8c49787a3