How many joules are in a kilowatt-hour?

One kilowatt-hour is 3,600,000 joules (3.6 MJ), because a kilowatt is 1000 watts and an hour is 3600 seconds (1000 × 3600). The kWh is the unit on your electricity bill. So 1 kWh also equals 3600 kJ, 860.42 kcal, or 3412.14 BTU.

Is a food Calorie the same as a calorie?

The 'Calorie' on nutrition labels (capital C) is actually a kilocalorie — 1000 small calories. So a 250-Calorie snack is 250 kcal = 1,046,000 joules. This converter labels kcal separately from cal to avoid that factor-of-1000 confusion, which is the most common energy-unit mistake.

How do I convert BTU to joules?

Multiply BTU by 1055.06 (1 BTU = 1055.05585 J). So a 10,000 BTU air conditioner output is about 10.55 MJ per hour of operation. To convert joules to BTU, divide by 1055.06. The BTU is common in US heating and cooling specifications.

How many calories are in a kilojoule?

One kilojoule is 0.239006 kilocalories (food Calories), since 1 kcal = 4.184 kJ. So a food labelled 2000 kJ contains about 478 Calories. Many countries print both kJ and Calories on packaging — this converter moves between them instantly.

Which calorie does this use?

It uses the thermochemical calorie, where 1 cal = 4.184 J exactly and 1 kcal = 4184 J. This is the standard for nutrition and chemistry. A slightly different 'international table' calorie (4.1868 J) exists in some engineering contexts, but the difference is under 0.1% and rarely matters in practice.

Energy Converter — joules, kWh, calories, BTU

From	Equals
1 kJ	0.239006 kcal · 0.277778 Wh
1 kcal	4184 J · 3.96567 BTU
1 BTU	1055.06 J · 0.293071 Wh
1 kWh	3.6 MJ · 3412.14 BTU

An energy converter moves a value between the units used across physics (joules), electricity (watt-hours, kWh), nutrition (calories, kilocalories) and heating (BTU). It converts your value into a base unit — joules — and back out. The classic trap it removes is the calorie confusion: the "Calorie" on a food label is a kilocalorie (1000 small calories), so this tool labels cal and kcal separately to keep you a factor of 1000 honest.

Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: SI and thermochemical energy factors, recomputed in code.

How the conversion works

Via a base unit

result = value × factor(from) ÷ factor(to) (factor = joules per unit)

Key factors

1 Wh = 3600 J · 1 kWh = 3.6 MJ · 1 cal = 4.184 J · 1 kcal = 4184 J · 1 BTU = 1055.06 J

Each unit equals a fixed number of joules: a watt-hour is 3600 J, a kilowatt-hour 3.6 million J, a kilocalorie 4184 J, a BTU 1055.06 J. Multiply your value by the "from" unit's joules-per-unit to reach joules, then divide by the "to" unit's. The kWh, the unit on your power bill, ties electrical energy to the rest: 1 kWh is the energy of running a 1000-watt appliance for one hour.

Worked example — 1 kWh in other units

Scenario: convert 1 kilowatt-hour to other energy units.

To joules

1 × 3,600,000 = 3,600,000 J (3.6 MJ)

To BTU

3,600,000 ÷ 1055.06 = 3412.14 BTU

To kilocalories

3,600,000 ÷ 4184 = 860.42 kcal

One kWh is 3,600,000 joules (3.6 MJ), 3412.14 BTU, or 860.42 kcal. The everyday cases follow the same rule: a 2000-kJ food label is about 478 Calories (kcal), 1 BTU is 1055 J, and 1 kcal is 4184 J. The converter shows your value in every unit at once, useful for energy bills, nutrition and engineering alike.

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Frequently Asked Questions

Joules in a kWh?⌄

3,600,000 J (3.6 MJ). 1 kWh = 3412.14 BTU = 860.42 kcal.

Food Calorie vs calorie?⌄

The label "Calorie" is a kilocalorie (1000 cal). 250 Cal = 250 kcal = 1.046 MJ.

BTU to joules?⌄

× 1055.06. 1 BTU = 1055.06 J = 0.293071 Wh.

Calories in a kJ?⌄

0.239006 kcal. A 2000 kJ food ≈ 478 Calories.

Which calorie?⌄

Thermochemical: 1 cal = 4.184 J, 1 kcal = 4184 J.

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