Energy Converter
Convert joules, kWh, calories, BTU, eV & 25+ energy units instantly. Used by engineers, physicists & nutritionists. Free, no sign-up required.
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Frequently Asked Questions
Clear answers to common questions to help you use this calculator confidently.
How do I convert joules to kilowatt-hours?
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How do I convert joules to kilowatt-hours?
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Divide joules by 3,600,000. Example: 3,600,000 J ÷ 3,600,000 = 1 kWh. This is the conversion behind electricity billing, since 1 kWh is the energy a 1,000-watt appliance uses in one hour.
What is 1 kWh in joules?
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What is 1 kWh in joules?
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1 kWh = 3,600,000 J (3.6 MJ). To go the other way, divide joules by 3,600,000 to get kWh.
What is the difference between calorie (cal) and Calorie (kcal)?
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What is the difference between calorie (cal) and Calorie (kcal)?
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The small calorie (cal) equals 4.184 J. The food Calorie on nutrition labels (capital C) is actually 1 kilocalorie (kcal) = 1,000 cal = 4,184 J. Mixing these up is a common source of error.
How do I convert BTU to joules?
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How do I convert BTU to joules?
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Multiply BTU by 1,055.06. Example: 1 BTU = 1,055.06 J. This is commonly used in HVAC and heating/cooling calculations.
How accurate is this energy converter?
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How accurate is this energy converter?
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It uses exact, internationally defined conversion factors (e.g. 1 kWh = 3,600,000 J exactly, 1 eV = 1.602176634 × 10⁻¹⁹ J), so results are precise to the number of decimal places you choose. For regulatory energy reporting, verify figures with a certified reference.
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