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ToolWrenConvert energy between joules, calories, kilocalories, watt-hours, kilowatt-hours and BTU.
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Energy is a free, private online tool that lets you convert energy between joules, calories, kilocalories, watt-hours, kWh and BTU. It runs entirely in your browser, so nothing you enter is uploaded to a server.
Privacy: this tool runs entirely in your browser. Your input is never sent to, received by, or stored on any server — there are no uploads and no tracking of what you enter.
Joules (SI), calories and kilocalories (food and chemistry), watt-hours and kWh (electricity bills) and BTU (heating and cooling).
1 kcal = 4184 J. 1 kWh = 3.6 million J. 1 BTU is about 1055 J.
Reading food energy, estimating electricity costs, and HVAC calculations.
Energy is the capacity to do work, and it shows up under many names across science, nutrition and utilities. The SI unit is the joule, but food labels use calories and kilocalories, electricity bills use watt-hours and kilowatt-hours, and heating and cooling use BTU. This converter ties them all to a common base.
Every unit is expressed relative to the joule, so conversion is convert-to-joules then convert-out. The key ratios: 1 calorie = 4.184 J, 1 kilocalorie (a food 'Calorie') = 4184 J, 1 watt-hour = 3600 J, 1 kilowatt-hour = 3.6 million J, and 1 BTU ≈ 1055 J. Those few numbers connect the worlds of physics, food and power bills.
A nutritional 'Calorie' with a capital C is actually a kilocalorie — 1000 small calories, or 4184 joules. So a 250-Calorie snack holds about 1.05 million joules of energy. Many countries print both kcal and kJ on labels; converting between them is a frequent everyday look-up this tool handles instantly.
Your electricity meter counts kilowatt-hours — the energy used by a 1000-watt appliance running for one hour, equal to 3.6 million joules. Converting kWh to joules or to BTU is useful for comparing appliance ratings, estimating running costs, and sizing heating or solar systems.
Read food energy in kcal or kJ, estimate electricity usage and costs, convert heating and air-conditioning capacities in BTU, and solve physics problems in joules. Everything is calculated locally in your browser.