THE NUMORIX GUIDE
How to use the Energy Converter
Last reviewed September 14, 2026
What this calculator does
Multiply by the selected unit's joule factor, then divide by each supported factor to produce J, kJ, cal, kcal, Wh, kWh, BTU, and eV outputs.
Formula and method
Multiply by the selected unit's joule factor, then divide by each supported factor to produce J, kJ, cal, kcal, Wh, kWh, BTU, and eV outputs.
Variables and inputs
Value defaults to 1 and the source unit defaults to kWh. The output uses energy units; calories are the thermochemical 4.184 J value in the engine.
Worked example
For 1 kWh: joules = 1 * 3,600,000 = 3.6e6 J; kcal = 3,600,000/4184 = 860.42 kcal; Wh = 1000 Wh; eV = about 2.247e25 eV.
How to interpret the result
Energy is conserved across the representation change. A kWh is a quantity of energy, not a rate of using energy; power is energy per time.
Common mistakes to avoid
Do not call kW an energy unit, and do not use a food Calorie conversion without remembering that one kilocalorie equals one dietary Calorie.
Assumptions and limitations
BTU and calorie definitions vary by convention; this engine uses one fixed factor. Display precision is limited by JavaScript Number and the formatter.
Practical use and checks
Use the Energy Converter when the same energy appears in different technical contexts, such as joules in physics, kilowatt-hours on an electricity bill, or kilocalories in nutrition. Enter 1 kWh as a check; the result should be 3,600,000 joules and 1,000 Wh, with about 860.42 kilocalories. That is energy, not power: 1 kW describes a rate, while 1 kWh describes the amount delivered by 1 kW over one hour. The converter keeps the physical quantity constant while changing its numerical label. Choose the category and source unit carefully, especially when a value is copied from a label that uses Calorie with a capital C. In nutrition, one food Calorie conventionally means one kilocalorie, but the context should still be stated. Calorie and BTU definitions can vary slightly, and this engine uses fixed factors, so a last-digit difference from another reference may reflect convention rather than a calculation error. The tool does not model efficiency, heat loss, intensity, or how long a device operates. It also cannot tell whether a claimed energy value is measured or estimated. When planning a bill or a thermal process, convert the quantity first, then apply the relevant time, efficiency, and uncertainty assumptions separately.