Energy Converter

A small calorie (cal) is the energy to raise 1 gram of water by 1 °C, equal to 4.184 joules. A kilocalorie (kcal) is 1,000 small calories ≈ 4,184 J. Food labels use kcal but commonly write 'Calories' (capital C). A 500-Calorie meal is 500 kcal, not 500 cal. The 1,000x difference matters.

The joule (J) is the SI unit of energy. 1 joule is the energy to apply 1 newton of force over 1 meter, or to pass 1 amp through 1 ohm for 1 second. It's a small unit: 1 food Calorie is over 4,000 J. Most everyday quantities are easier in kJ or kcal.

1 kWh is the energy used by a 1,000-watt appliance running for 1 hour, equal to 3.6 megajoules. It's the standard unit on residential electric bills. Running a 100 W lightbulb for 10 hours uses 1 kWh.

British Thermal Unit. 1 BTU is the energy to raise 1 pound of water by 1 °F, about 1,055 joules. Used in HVAC sizing (a 12,000 BTU/h air conditioner) and heating. 1 BTU/h is a unit of power, not energy.

Yes, in unit-conversion math. Energy is energy regardless of label. They are interchangeable in calculations as long as you respect the conversion factors. The difference is convention: chemists use kJ/mol, nutritionists use kcal, electric utilities use kWh, HVAC engineers use BTU.

Both. The calculator does pure unit conversion; it does not give nutrition advice or thermodynamics interpretation. If you see 'Calories' on a food label, that's kcal. If you see 'kcal/mol' in a chemistry context, that's the same kcal × Avogadro's number.