Energy Converter
Our free conversions & measurement calculator solves energy problems. Get worked examples, visual aids, and downloadable results.
Reviewed by Manoj Kumar, Mathematics Educator
Formula
1 cal = 4.184 J | 1 kWh = 3,600,000 J | 1 BTU = 1055.06 J | 1 eV = 1.602e-19 J
The joule (J) is the SI unit of energy, defined as the work done when a force of one newton moves an object one meter. All other energy units convert to joules through a fixed, internationally agreed factor: calories via the mechanical equivalent of heat, kilowatt-hours via power multiplied by time, BTU via the heat needed to warm one pound of water by one degree Fahrenheit, and electronvolts via the charge of a single electron.
Worked Examples
Example 1: Electricity Bill Energy Use
Problem:A household appliance uses 1 kWh of electricity. Express this in joules, calories, and BTU.
Solution:Joules = 1 kWh x 3,600,000 J/kWh = 3,600,000 J\nCalories = 3,600,000 / 4.184 = 860,421 cal\nBTU = 3,600,000 / 1055.06 = 3,412.14 BTU
Result:1 kWh = 3,600,000 J = 860,421 cal = 3,412.14 BTU
Example 2: Food Energy to Joules
Problem:A snack bar contains 180 food Calories (kcal). Convert this to joules and kilojoules.
Solution:Joules = 180 kcal x 4184 J/kcal = 753,120 J\nKilojoules = 753,120 / 1000 = 753.12 kJ
Result:180 Calories = 753,120 J = 753.12 kJ
Example 3: Particle Physics Energy Scale
Problem:A particle accelerator imparts 2.5 MeV of kinetic energy to an electron. Convert this to joules.
Solution:1 MeV = 1,000,000 eV x 1.602e-19 J/eV = 1.602e-13 J\n2.5 MeV = 2.5 x 1.602e-13 = 4.005e-13 J
Result:2.5 MeV = 4.005 x 10^-13 joules
References
Reviewed by Manoj Kumar, Mathematics Educator · Editorial policy