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Units and conversions

Energy Converter

Convert an energy amount and compare its equivalent in eight units.

Convert an energy amount

Use a decimal such as 1.5 or a grouped number such as 1,000. Zero and signed energy changes are accepted. Do not include units or expressions.

Swap units exchanges the selections and keeps the entered number.

Example: 1 kWh → 3.6 MJ.

Converted energy

Enter an energy amount, choose two units, then select Convert.

Conversions run in your browser. Press Enter to convert. Successful conversions appear in this tab’s Recent calculations.

Need heat for a temperature change? Use the Heat Energy Calculator with mass and specific heat capacity.

Energy conversion examples

Electricity

2.5 kWh in megajoules

2.5 × 3.6 = 9 MJ

Convert an electricity reading to SI energy units. Both quantities represent the same energy amount.

Thermochemical calories

100 kcal in kilojoules

100 × 4.184 = 418.4 kJ

The conversion uses thermochemical kilocalories. It does not calculate a person’s dietary needs.

Heating

1 BTU IT in joules

1 BTU IT = 1,055.05585262 J

This is the exact IT conversion factor. It is not the thermochemical BTU or a rating in BTU per hour.

Conversion method and definitions

First convert the source amount to joules, then divide by the joules represented by one target unit: target amount = source amount × source factor ÷ target factor. These factors are exact: 1 kJ = 1,000 J; 1 MJ = 1,000,000 J; 1 Wh = 3,600 J; 1 kWh = 3,600,000 J; 1 thermochemical cal = 4.184 J; 1 thermochemical kcal = 4,184 J; and 1 BTU IT = 1,055.05585262 J.

Exact integer fractions retain the entered decimal and unit ratios. Only the visible results are rounded, with exact halfway values rounded away from zero. ≈ indicates display rounding, and trailing decimal zeros are omitted. A nonzero value can round to zero; choose more decimal places or a smaller output unit to inspect it. Conversions preserve the sign of an energy change.

Inputs allow at most 64 characters, 15 integer digits, and 10 decimal places. Correctly grouped thousands commas are accepted. Scientific notation, currency symbols, expressions, and unit text in the amount field are rejected. Maximum decimal places can be 0, 2, 4, 6, or 10. Changing the target unit or display precision uses the original unrounded amount and does not add a recent-calculation entry.

A unit conversion does not infer efficiency, heat loss, operating time, fuel content, or appliance cost. A power quantity such as W, kW, or BTU/h requires a time interval to obtain energy. Measured values retain their original measurement uncertainty regardless of how many digits you display.

References: NIST Guide to the SI — energy conversion factors and NIST — calorie and exact BTU definitions.

Common questions

Is a food Calorie the same as a calorie?

A food Calorie commonly refers to a kilocalorie, which is 1,000 small calories. Select the kilocalorie option when that is what your label means. This tool uses thermochemical calories; another stated calorie definition may have a different joule factor.

Can I convert kilowatts directly to kilowatt-hours?

You need a duration. For constant power, energy in kWh = power in kW × time in hours. Use the Power Calculator for that calculation, then convert the resulting energy here.

Does BTU mean BTU per hour?

BTU is energy. BTU/h is power. This converter handles energy amounts in International Table BTU and does not treat a heating or cooling power rating as an energy total.

Why are negative values accepted?

A negative number can describe an energy change or transfer under a chosen sign convention. Unit conversion preserves that sign. It does not determine whether the sign is appropriate for your physical model.