Energy Conversion Calculator — Joules, kWh, BTU, kcal & More
Convert any energy value between Joules, kilowatt-hours, calories, BTU, foot-pounds, ergs and more. Enter an amount, choose the source unit and the target unit — the result appears immediately along with reference values in all supported units.
From unit
To unit
Result in the selected output unit
- 1
Energy in Joules
1 × 3,600,000 = 3,600,000 J1 kWh = 3,600,000 J — multiply to convert to the canonical base unit. - 2
Convert to MJ
3,600,000 ÷ 1,000,000 = 3.600000
How does this calculator work?
All energy conversions go through Joules: multiply your value by the source unit's Joule factor, then divide by the target unit's factor. For example, 1 kWh = 3.6 MJ = 860 kcal ≈ 3 412 BTU. Select any two units and enter an amount to convert instantly across 10 common energy units.
Formula
How this is calculated
All energy conversions reduce to a common base unit — the Joule (J). Every unit has a fixed ratio to the Joule (e.g. 1 kWh = 3 600 000 J; 1 BTU ≈ 1 055.06 J; 1 kcal = 4 184 J). To convert from unit A to unit B, the calculator first multiplies the input value by A's Joule factor to get the energy in Joules, then divides by B's Joule factor.
The calorie used here is the thermochemical calorie (1 cal = 4.184 J), which matches scientific and food-label usage (1 kcal = 1 food Calorie). The BTU is the international table BTU (≈ 1 055.06 J). The foot-pound is the standard mechanical foot-pound (≈ 1.3558 J). The erg is the CGS unit (1 erg = 10⁻⁷ J), used in older physics literature.
The bar chart shows all units on a logarithmic scale because energy values span many orders of magnitude — for example, 1 kWh equals 3 600 000 J but only 0.86 kcal in the wrong direction. Reading the bar chart visually shows relative magnitudes across the full unit range.
Frequently asked questions
One kilowatt-hour (kWh) equals exactly 3 600 000 Joules (3.6 MJ). This follows from the definition: 1 W = 1 J/s, so 1 kW = 1 000 J/s, and 1 kWh = 1 000 J/s × 3 600 s = 3.6 × 10⁶ J.
One kilocalorie (kcal) = 1 000 calories. Food nutrition labels use "Calories" (capital C) to mean kilocalories — so a 200 Calorie snack contains 200 kcal or 200 000 cal. Both the calorie and kilocalorie here use the thermochemical definition (1 cal = 4.184 J).
1 BTU ≈ 1 055.06 J and 1 kWh = 3 600 000 J, so 1 BTU ≈ 2.931 × 10⁻⁴ kWh. Equivalently, 1 kWh ≈ 3 412 BTU. These ratios are used for heating/cooling system comparisons.
TG we-Calculate Editorial Team. (2026). Energy Conversion Calculator — Joules, kWh, BTU, kcal & More [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/energy-conversion-calculator
TG we-Calculate Editorial Team. "Energy Conversion Calculator — Joules, kWh, BTU, kcal & More." TG we-Calculate. 2026. https://we-calculate.com/calculator/energy-conversion-calculator.
TG we-Calculate Editorial Team, "Energy Conversion Calculator — Joules, kWh, BTU, kcal & More," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/energy-conversion-calculator
@misc{wecalculate_energy_conversion_calculator, title = {Energy Conversion Calculator — Joules, kWh, BTU, kcal & More}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/energy-conversion-calculator}}, year = {2026}, note = {TG we-Calculate} }
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