What is Energy Converter?

Energy Converter translates between joules, kilojoules, calories, kilocalories, kilowatt-hours, BTUs, and more. Useful for physics homework, nutrition science, engineering calculations, and utility bill analysis.

The converter spans thirteen units grouped by domain: SI (J, kJ, MJ, GJ), calorie (cal, kcal), electrical (Wh, kWh), thermal (BTU, therm), mechanical (ft·lb, erg), and atomic (eV). It's tuned for cross-domain conversions where most calculators stop, like comparing a food label in kcal to a battery rating in Wh, or a furnace spec in BTU to a heat pump's kWh draw.

How to use

1. Enter a value and select the source energy unit.
2. View instant conversions across all supported energy units.
3. Pick a decimal precision, then copy a single value, copy them all, or grab a share link that re-opens the same conversion.

When to use

• Converting a kWh electricity bill into kcal or BTU for back-of-envelope comparisons.
• Cross-checking food-label calories against the joules used in physics problems.
• Sizing batteries by translating mAh × voltage into watt-hours and then joules.

Result

Convert 2,000 kcal (a day's food intake) to see it equals 8,368 kJ or 2.33 kWh — enough energy to run a 100W lightbulb for 23 hours.

FAQ

Is one Calorie on a food label the same as one calorie in physics?

No. The dietary Calorie (capital C) is a kilocalorie, equal to 1,000 small calories. A 200-Calorie snack is 200,000 calories or about 837 kilojoules. The converter uses lowercase cal, so enter 200,000 or use the kcal field directly.

How many joules are in a kilowatt-hour?

Exactly 3,600,000 joules. A kilowatt is 1,000 joules per second, and one hour is 3,600 seconds. That's why a 1 kWh utility unit looks small on a bill but represents enough energy to lift a small car 360 metres straight up.

When should I use BTU instead of joules?

Heating, cooling, and gas appliances in North America are still rated in BTU per hour. One BTU is 1,055 joules. A 12,000 BTU/hour air conditioner is therefore a 3.5 kW unit, useful when comparing US specs to European equivalents.

What's an electronvolt and when does it matter?

An electronvolt is the energy gained by one electron crossing a one-volt potential difference, about 1.6 × 10⁻¹⁹ joules. It's the working unit of particle physics, photon energies, and semiconductor band gaps where joule values would be unreadably small.

Why do my kcal and kJ figures on European food labels not divide cleanly by 4.184?

EU regulations round both values independently to whole numbers, so a 100 kcal bar might list 418 kJ instead of 418.4. The converter uses the exact factor 4.184, so a tiny rounding gap against the printed label is expected.

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