Energy Conversion Calculator
Written by Thierno Sadou Diallo, formula verified per our methodology • Last checked on 9/5/2026
To convert energy, it's brought back to a common unit (the joule) then converted into the new unit. For example, 1 kWh represents about 860.42 kilocalories.
Explanation
Energy is measured in very different units depending on the field: the joule (J) is the International System unit, used in physics; the calorie (cal) and especially the kilocalorie (kcal, often simply called a 'calorie' on food labels) are used to express the energy provided by food; the kilowatt-hour (kWh) is the reference unit for electrical energy, the one shown on an electricity bill; the BTU (British Thermal Unit) is still used in the United States, particularly for air conditioner and heater power ratings. Converting energy amounts to multiplying the value by the factor that brings it back to joules, then dividing by the target unit's factor — exactly what this calculator does. The calorie used here is the thermochemical calorie (exactly 4.184 J), the most common definition; the BTU used is the International Table BTU (1055.06 J), slightly different from the thermochemical BTU, the gap remaining negligible for everyday use. To directly convert electrical power into a cost on your bill, see our electricity consumption calculator; for the calories associated with a meal's macronutrients, our macronutrient calorie calculator.
Example: converting 1 kWh to kilocalories
Inputs
Value: 1. Starting unit: kWh. Target unit: kcal.
Calculation
1 kWh = 1 × 3,600,000 J. In kilocalories: 3,600,000 ÷ 4184 ≈ 860.42 kcal.
Result
1 kWh represents about 860.42 kilocalories.
Frequently asked questions
Why are food calories actually kilocalories?
On food labels, the term 'calorie' (often capitalized as 'Calorie' in English-speaking countries) actually refers to the kilocalorie (1000 calories), a simplification that has become common usage. A kilocalorie (kcal) corresponds to the energy needed to raise the temperature of 1 liter of water by 1 °C, a definition far more intuitive at the scale of a meal than the base calorie, a thousand times smaller.
Why is kWh used rather than the joule on an electricity bill?
Because the joule is far too small a unit for household use: an electricity bill in joules would show numbers with several million digits. The kilowatt-hour corresponds to the energy consumed by a 1000-watt appliance running for 1 hour, a much more readable scale for a household's consumption over a month.
Is the BTU used here the same everywhere?
This calculator uses the International Table BTU (1055.05585262 J), the most widely used definition today, notably for air conditioners and heaters in the United States. Other historical definitions of the BTU exist (thermochemical, at 39°F...) with a gap of around 0.1%, negligible for everyday use.