Free Energy Converter
Convert between joules, calories, kilocalories, kWh, BTU, foot-pounds, and electronvolts. Instant energy unit conversion calculator.
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1 Kilowatt-hours =
Formula
Converted Value = Input Value × (Source Unit in joules) ÷ (Target Unit in joules)How to Convert Energy Units
Energy conversion normalizes all values to joules (the SI unit of energy), then converts to your target unit. This converter covers everything from food calories to electrical energy to particle physics.
Energy Units Explained
- Joules (J) — the SI unit of energy. The energy needed to exert 1 newton of force over 1 meter.
- Kilojoules (kJ) — 1,000 joules. Often used on food labels outside the US.
- Calories (cal) — the energy to raise 1 gram of water by 1°C. Equal to 4.184 joules.
- Kilocalories (kcal) — 1,000 calories. This is the "Calorie" on food nutrition labels.
- Kilowatt-hours (kWh) — the standard billing unit for electricity. 1 kWh = 3.6 million joules.
- BTU — British Thermal Units, used for HVAC systems and natural gas. 1 BTU ≈ 1,055 joules.
- Foot-pounds (ft·lbf) — used in engineering and ballistics. 1 ft·lbf ≈ 1.356 joules.
- Electronvolts (eV) — tiny energy unit used in atomic and particle physics.
Common Energy References
- Apple: ~95 kcal (398 kJ)
- Running 1 mile: ~100 kcal (418 kJ)
- 1 gallon of gasoline: ~132,000 BTU (139 MJ)
- Lightning bolt: ~1 billion joules (278 kWh)
Frequently Asked Questions
What is the difference between a calorie and a kilocalorie?
A kilocalorie (kcal) is 1,000 calories. Food 'Calories' (capital C) are actually kilocalories. So a 200 Calorie food item contains 200 kcal or 200,000 calories (small c).
How do I convert kWh to BTU?
Multiply kWh by 3,412.14 to get BTU. For example, 1 kWh = 3,412.14 BTU. This is useful for comparing electricity costs with natural gas heating costs.
What is an electronvolt?
An electronvolt (eV) is the energy gained by an electron moving through 1 volt of potential difference. It equals 1.602 × 10⁻¹⁹ joules. Used in particle physics and semiconductor science.
How much energy does a household use?
The average US household uses about 30 kWh per day or 900 kWh per month. That's about 3.24 billion joules or 3.07 million BTU per month.
What is a BTU?
A British Thermal Unit (BTU) is the energy needed to raise 1 pound of water by 1°F. It equals about 1,055 joules. BTU is commonly used for heating/cooling capacity and natural gas billing.