Energy Converter
Convert joules, calories, kWh, BTU, electron-volts and more.
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Joule (J)
Kilojoule (kJ)
| Unit | 1 J equals |
|---|---|
| Joule (J) | 1 |
| Kilojoule (kJ) | 0.001 |
| Calorie (cal) | 0.239006 |
| Kilocalorie (kcal) | 0.000239006 |
| Watt Hour (Wh) | 0.000277778 |
| Kilowatt Hour (kWh) | 2.77778e-7 |
| BTU (BTU) | 0.000947813 |
| Electron Volt (eV) | 6.24151e+18 |
| Foot-Pound (ft·lb) | 0.737561 |
How it works
- 1 kcal = 4,184 J
- 1 kWh = 3,600,000 J
- 1 BTU ≈ 1,055 J
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Frequently asked
How many joules in a kilocalorie?
1 kcal = 4,184 J.
Where you'll actually use this
Energy converters bridge joules, calories, kilowatt-hours, BTUs, and electron-volts — the same physical quantity expressed for science, nutrition, electricity, or HVAC.
- Electricity bills
Usage is billed in kWh. Convert to joules for physics, or to BTU for HVAC comparisons.
- Nutrition
Food 'calories' are actually kilocalories (kcal). 1 kcal = 4,184 J. EU labels list both kcal and kJ.
- HVAC & cooling
Air conditioner output is quoted in BTU/h in the US, watts elsewhere.
Common mistakes to avoid
- Calories vs kilocalories
When a food label says '250 calories' it really means 250 kcal = 250,000 small calories.
- kW vs kWh
kW is power (rate); kWh is energy (total). A 1 kW heater running for 2 hours uses 2 kWh.
Did you know?
A typical modern fridge uses about 1 kWh per 24 hours — roughly $0.10–$0.30 depending on local rates.
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Accuracy & sources
How this tool is built and verified.
- Source
- Standards-aligned factors
- Last reviewed
- Q2 2026
- Status
- Verified
- International System of Units (SI)BIPM — Bureau International des Poids et Mesures · The International System of Units (SI Brochure), 9th edition
- ISO 80000 — Quantities and UnitsISO / IEC · ISO 80000-1:2022
- Standards aligned
- Formula verified
- Editor reviewed
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