§ 01 / TOOL
Energy Converter.
STATUS READYUNITS 9BASE JOULE
> CONVERT
// FROM
=
// TO
418.4
RESULT.
kcal → kJ
418.4 kJ.
100 kcal = 418.4 kJ
§ 02 / ABOUT
How it works.
Energy is the capacity to do work. The SI unit is the joule (J) — one newton-meter, the energy to lift 100 grams about 1 meter against gravity. Different fields use different units; the math is the same.
// THE KEY CONVERSIONS
- 1 small calorie = 4.184 J
- 1 food Calorie / kcal = 1,000 small calories = 4,184 J = 4.184 kJ
- 1 Wh = 3,600 J
- 1 kWh = 3.6 MJ = 860 kcal
- 1 BTU = 1,055.06 J = 0.252 kcal
// USE IT FOR
- Nutrition — translating Calories on US labels to kJ on EU/AU labels.
- Electric bills — kWh ↔ joules for back-of-envelope appliance math.
- HVAC — BTU/h ratings translated to watts (1 watt ≈ 3.412 BTU/h).
- Physics + engineering — joules as the universal currency for work, heat, and electrical energy.
§ 03 / FAQ
Common questions.
What’s the difference between calorie and Calorie?+
A "small calorie" (cal) is the energy to raise 1 gram of water 1°C — about 4.184 joules. A "food Calorie" (Cal, capital C, also written kcal) is 1,000 small calories = 4,184 joules. Nutrition labels in the US say "Calories" but mean kilocalories. The 2,000 Calories/day diet is really 2,000,000 small calories or 8.4 megajoules.
How is kWh on my electric bill calculated?+
A kilowatt-hour is the energy of running a 1,000-watt appliance for one hour. So 3,600,000 joules. A typical US home uses ~30 kWh/day. At $0.15/kWh (US average), that’s about $135/month for the average household.
What’s a BTU?+
British thermal unit — the energy to raise 1 pound of water by 1°F. Equals 1,055.056 joules. Used in HVAC ratings (a 12,000 BTU/h air conditioner moves 12,000 BTU of heat per hour) and in US natural-gas billing.
How do I convert kcal to kJ for nutrition?+
Multiply by 4.184. So a 100 Calorie (kcal) snack is 418.4 kilojoules. EU and Australian food labels show both; US labels show only Calories.
§ 04 / TOOLS
Related calculators.
§ 05 / READING