Energy Converter

Convert a fixed amount of energy

Enter a finite amount and choose both units. Every conversion passes through joules. Watt-hours and kilowatt-hours are energy units here, while rates such as watts or BTU per hour belong in the Power Converter.

Units included

The converter includes joules, kilojoules, megajoules, watt-hours, kilowatt-hours, International Table BTU, thermochemical calories, and kilocalories. Prefixes matter: one kilojoule is 1,000 joules, and one megajoule is 1,000,000 joules.

Watt-hours are energy

A watt-hour combines a power rate with time. One watt sustained for one hour transfers 3,600 joules, so one kilowatt-hour equals 3.6 million joules. Utility bills commonly price electrical energy in kilowatt-hours, though the bill can also contain fixed charges, demand charges, taxes, and tiers.

Calories can be ambiguous

This page labels thermochemical calorie and kilocalorie. One thermochemical calorie equals 4.184 joules, and one kilocalorie equals 4,184 joules. Food labels often use “Calorie” with a capital C to mean a kilocalorie, but this arithmetic tool does not interpret nutrition or metabolism.

Worked example

Convert 2.5 kilowatt-hours to megajoules. Each kilowatt-hour equals 3.6 megajoules, so multiplying 2.5 by 3.6 gives 9 megajoules. That is an energy amount; it does not reveal how quickly the energy was used.

BTU definition

The conversion uses the International Table BTU, approximately 1,055.05585262 joules. Other historical or context-specific BTU definitions differ slightly. Keep the source definition when reproducing a regulated, scientific, or contractual calculation.

Limitations and precision

Results use JavaScript floating-point numbers and show up to twelve significant digits. The page does not calculate efficiency, heat loss, fuel composition, emissions, utility price, battery usable capacity, or device runtime. Negative values remain available for signed accounting, but physical context determines whether they make sense.