Fidamen

Convert Kilojoules to Kilocalories – Energy Converter

Quickly convert energy values from kilojoules (kJ) to kilocalories (kcal). This calculator is intended for everyday tasks—food labels, recipes, and basic lab bookkeeping—and uses SI-consistent definitions to avoid ambiguity.

In nutrition contexts the kilocalorie (kcal) is commonly shown as “Calorie” (capital C). In physics and engineering contexts the kilojoule (kJ) is the SI energy unit commonly used. This tool translates between them using the standard thermochemical definition.

Results are suitable for planning and record-keeping. For metrology-grade measurements (e.g., calorimetry research or regulated reporting) follow instrument calibration and uncertainty procedures described by national measurement authorities.

Updated Nov 28, 2025QA PASS — golden 25 / edge 120Run golden-edge-2026-01-23

Governance

Record beb0d20ec9eb • Reviewed by Fidamen Standards Committee

Interactive Converter

Convert between kilojoule and kilocalorie with precision rounding.

Quick reference table

KilojouleKilocalorie
1 kJ4.18 kcal
5 kJ20.92 kcal
10 kJ41.84 kcal
25 kJ104.6 kcal
50 kJ209.2 kcal
100 kJ418.4 kcal

Methodology

The conversion is based on the internationally adopted thermochemical definition: 1 kilocalorie (1 kcal) = 4184 joules (J) = 4.184 kilojoules (kJ). This is the value used by national metrology bodies.

To convert kJ to kcal we apply the fixed mathematical relationship (divide kJ by 4.184). The calculator performs that operation and presents results with reasonable default rounding while preserving accuracy.

When using converted values for regulated reporting, lab records, or publication cite the originating measurement and report measurement uncertainty and calibration status according to guidance from national standards bodies.

Worked examples

100 kJ = 23.900 kcal (100 ÷ 4.184 = 23.900).

500 kJ = 119.501 kcal (500 ÷ 4.184 ≈ 119.501).

1000 kJ = 239.006 kcal (1000 ÷ 4.184 ≈ 239.006).

F.A.Q.

What is the exact relationship between kJ and kcal?

By convention 1 kilocalorie (kcal) = 4184 joules (J) = 4.184 kilojoules (kJ). Use the factor 4.184 when converting between kJ and kcal.

Why do nutrition labels say “Calories” instead of kcal?

Food energy on nutrition labels commonly uses the term Calorie (capital C) to mean kilocalorie. Numerically, 1 Calorie (nutrition) = 1 kcal = 4.184 kJ. When converting labels, treat food Calories as kilocalories.

When should I worry about rounding or significant figures?

For recipes and daily tracking 1–2 decimal places are usually fine. For laboratory and metrology work, round to reflect instrument precision and include measurement uncertainty; avoid giving false precision beyond the instrument's calibrated uncertainty.

Can I use this calculator for calorimeter data or regulatory reporting?

This converter provides the mathematical conversion only. For calorimetry or regulated reporting pair converted values with instrument calibration certificates and uncertainty analysis following guidance from national measurement institutes before submission.

Are there different definitions of the calorie?

Historically several calorie definitions existed (thermochemical, international steam-table, etc.). The thermochemical definition (1 cal_th = 4.184 J) is the convention most commonly used for kcal ↔ kJ conversions today; consult national standards for context-specific definitions.

How do I account for measurement error when converting?

Convert the nominal value then propagate the measurement uncertainty. If your energy measurement has ±Δ kJ, convert both nominal and uncertainty by dividing by 4.184 to get kcal and ±Δ kcal. For formal uncertainty analysis follow guidance from metrology organizations.

Sources & citations

Further resources

Versioning & Change Control

Audit record (versions, QA runs, reviewer sign-off, and evidence).

Record ID: beb0d20ec9eb

What changed (latest)

v1.0.0 • 2025-11-28 • 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 28, 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 • 2025-11-28 • 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: 853847caa005