How to Convert Joules to Coulombs

Updated February 21, 2017

Energy and work can be measured using the SI unit of the joule, named for the British physicist James Prescott Joule. Electrical charge is measured in another SI unit, the coulomb, named for the French physicist, Charles-Augustin de Coulomb. The two units are linked via electrical potential, which is measured in joules per coulomb. Since electrical potential is measured in volts, it is possible to convert joules to coulombs when the voltage is known.

Enter the number of joules into the calculator. For example; if the amount of work equates to 30 joules, enter 30 into the calculator.

Divide the value from Step 1 by the voltage. The result is the electrical charge measured in coulombs. If, for example, the voltage is 10 volts, and the amount of work is 30 joules, then the electrical charge is 3 coulombs (30 / 10 = 3).

Reverse the calculation to check for errors. Multiply the value in coulombs by the voltage. If the result is not the original value in joules, there was an error in the calculations. Repeat the calculations until the correct result is obtained.


The formula used to find coulombs when joules and the voltage are known is: Coulombs = Joules / Voltage. The formula is often seen as volts = joules / coulombs. The SI (System International) symbols for joules and coulombs are the capital letters J and C.

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About the Author

David Robinson has written professionally since 2000. He is a Fellow of the Royal Geographical Society and the Royal Meteorological Society. He has written for the "Telegraph" and "Guardian" newspapers in the U.K., government publications, websites, magazines and school textbooks. He holds an honors Bachelor of Arts in geography and education and a teaching certificate from Durham University, England.