Joules to Volts Calculator - Energy per Charge

Agarapu Ramesh — Editor and content reviewer
Editorially reviewed Reviewed by Agarapu Ramesh, science educator (chemistry). LinkedIn
Last reviewed: May 2026 | Standard electrical engineering formulas

Voltage is energy per charge. If you know the joules moved and the coulombs of charge, volts = joules / coulombs. Without the charge value, joules cannot be converted to volts.

Formula at a glance

  • V = J / C
  • J = V x C
  • C = J / V

Field note: The missing input is usually charge. If somebody says "convert 100 joules to volts" and gives nothing else, the right answer is to ask for coulombs.

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Joules to Volts Calculator

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Formula

V = J / C

How to use the Joules to Volts Calculator

Use this as a unit check for energy, power and time. Keep the time period honest, because a one-hour run and a one-month run can make the same load look completely different.

Worked example

Example: 24 J moved by 2 C of charge gives 12 V. Same energy with 6 C gives only 4 V.

Practical checks before you trust the number

  • Coulombs measure charge, not current. Current is coulombs per second.
  • For batteries, voltage changes with state of charge and load.
  • For capacitors, voltage also depends on capacitance and stored energy.

Common mistake

The missing input is usually charge. If somebody says "convert 100 joules to volts" and gives nothing else, the right answer is to ask for coulombs.

Sources and references

Related calculators

Frequently Asked Questions

V = J ÷ Q, where Q is electric charge in coulombs. Voltage is energy per unit charge. Example: 10 J across 2 C → V = 5 V. This is the fundamental definition of voltage as the work done per coulomb of charge moved through the potential difference.

V = E ÷ Q. Volts equal joules per coulomb. So 1 V means 1 joule of work done per coulomb of charge moved. Example: a 12 V battery delivering 1 C of charge releases 12 J of energy. This is the bedrock of all electrical energy calculations.

V = J ÷ Q = 10 ÷ 2 = 5 V. So 10 joules of energy spent moving 2 coulombs of charge corresponds to a 5-volt potential difference. This relationship lets you convert between energy and voltage when charge is known.

Because voltage is defined as energy per unit charge. Without charge, you can't relate joules (energy) to volts (potential difference). The two quantities are linked through Q, so any conversion needs the charge value to be physically meaningful.

Energy (J) is the total work done; voltage (V) is the work done per unit charge. Energy is an absolute quantity; voltage is a per-charge ratio. A capacitor stores energy E = ½CV², so voltage and energy are related through the capacitance and stored charge.

Yes. For a capacitor, E = ½CV², so V = √(2E ÷ C). Example: 1 J stored in a 100 µF cap → V = √(2 × 1 ÷ 0.0001) = 141 V. This is how engineers calculate the voltage on energy-storage capacitors in flash circuits and power converters.

Yes. The calculator shows that voltage is fundamentally an energy-per-charge ratio. This helps students grasp why a 1.5 V battery and a 12 V battery do different amounts of work per coulomb, and why higher voltage means more energy delivered per unit current. Powerful pedagogical tool.