Energy Converter

Supported energy units

The converter supports four units:

• Joules (J), the SI unit of energy
• Small calories (cal), where 1 cal equals 4.184 J
• Kilocalories (kcal), where 1 kcal equals 4,184 J
• Kilowatt-hours (kWh), where 1 kWh equals 3,600,000 J

Every conversion first maps the input to joules and then divides by the joule value of the selected output unit. Using one base table keeps conversions in opposite directions consistent.

Calories and food Calories

The word “calorie” is ambiguous. A small scientific calorie is written cal. Food labels commonly use “Calories” with a capital C to mean kilocalories, written kcal. One food Calorie therefore equals 1,000 small calories.

Select kilocalories when converting nutrition-label values. Select calories only when the source explicitly uses small calories.

Kilowatt-hours

A kilowatt-hour measures energy, not power. It is the energy used by a 1,000-watt device operating for one hour. Electricity bills and battery capacities often use watt-hours or kilowatt-hours, while physics calculations commonly use joules.

Precision and limits

Results are displayed in scientific notation with six digits after the decimal point. That display precision does not make an imprecise source measurement more accurate. Keep the original measurement and its stated uncertainty when the conversion is used for laboratory, engineering, nutrition, or billing work.