Energy converter: joules, calories, kWh and eV

Convert among joules (J), thermochemical calories (cal), kilowatt-hours (kWh) and electronvolts (eV). The calculation passes through joules using the factors listed below.

How to convert kWh to joules

Multiply energy in kWh by 3,600,000. One watt equals one joule per second, and one hour contains 3,600 seconds. Therefore, 1 kWh = 1,000 × 3,600 J = 3,600,000 J. Divide by the same factor to convert joules to kWh.

Worked example

2.5 kWh × 3,600,000 = 9,000,000 J. Enter 2.5, choose kWh as the source unit and J as the result unit. Scientific notation such as 9.000000e+6 means nine million.

Conversion factors used

• 1 J is the reference unit.
• 1 thermochemical cal = 4.184 J; this is the calorie convention used here.
• 1 kWh = 3,600,000 J.
• 1 eV = 1.602176634 × 10⁻¹⁹ J.

The tool converts through joules: value × source factor ÷ target factor. 500 cal = 2,092 J. A kilocalorie equals 1,000 calories; 500 kcal would be 2,092,000 J. The selector offers cal, not kcal.

kW and kWh: power and energy

kW measures power; kWh measures energy. To estimate energy at constant power, multiply kW by operating hours. A hypothetical 1.5 kW appliance used for two hours consumes 3 kWh, or 10,800,000 J.

Cost also depends on the electricity tariff. At a hypothetical rate of R$0.80 per kWh, the energy portion of that example would be R$2.40. Taxes and other bill items may change the total. This tool converts units and does not estimate an electricity bill.

Check the result before using it

Use finite numbers and units of the same physical quantity. The displayed result is rounded, and calculations use the browser’s numeric precision. Converting the energy in food to joules does not show how much a device or the human body can use.

Factor reference: NIST — units accepted for use with the International System of Units.