What this calculator does
A joules to volts calculator cannot just multiply or divide by a fixed number, because joules and volts measure different things. A joule is a unit of energy. A volt is a unit of electric potential, which is energy per unit of electric charge. The two are only connected once you know how much charge is involved, which is why this calculator asks for a charge value in coulombs rather than converting energy on its own.
The relationship is V = E ÷ Q: voltage equals energy divided by charge. So a question like "200 joules to volts" has no single answer until a charge is specified, since 200 joules moving 1 coulomb of charge gives 200 volts, while 200 joules moving 10 coulombs gives only 20 volts. Enter the energy and the charge below and the voltage follows directly from that formula.
The formula
Divide the energy in joules by the electric charge in coulombs. The result is the voltage, since one volt is defined as one joule per coulomb. Change either input and the voltage recalculates immediately.
| Term | Meaning |
|---|---|
| Volt (V) | A unit of electric potential difference, equal to one joule of energy per coulomb of charge. |
| Joule (J) | The SI unit of energy or work. |
| Coulomb (C) | The SI unit of electric charge; the quantity that links energy and voltage together. |
The inputs explained
| Field | What to enter |
|---|---|
| Energy (J) | The amount of energy involved, in joules. |
| Electric charge (C) | The amount of electric charge the energy is moving, in coulombs. This must be a real, known value for the conversion to mean anything, since volts to joules and joules to volts both depend on it. |
When to use it
Checking a textbook problem
Physics and electronics problems often give energy and charge together and ask for the voltage, or give voltage and charge and ask for energy. Rearranging V = E ÷ Q covers the first case directly.
Sanity-checking a capacitor calculation
Capacitor energy problems frequently produce an energy figure in joules alongside a charge figure in coulombs. Dividing one by the other gives the voltage across the capacitor as a cross-check on other working.
Understanding why a plain unit conversion will not work
Someone searching for a fixed joules-to-volts multiplier will not find one, because none exists. Seeing the formula with an editable charge value makes clear why a charge figure is always required.
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
Voltage for 200 joules at different charge values
The same 200 joules of energy produces very different voltages depending on how much charge it is moving, which is the core reason a fixed conversion factor cannot exist.
Voltage for a fixed 5 coulomb charge at different energy levels
With charge fixed, voltage rises in direct proportion to energy.
Questions
How do you convert joules to volts?
You cannot convert joules to volts on their own, because they measure different physical quantities. Divide the energy in joules by the electric charge in coulombs that the energy is moving: V = E ÷ Q. You need a charge value to get a voltage.
What is 200 joules to volts?
It depends entirely on the charge involved. 200 joules moving 1 coulomb of charge is 200 volts, but 200 joules moving 5 coulombs is only 40 volts. There is no single fixed answer without knowing the charge.
How do you go from volts to joules?
Rearrange the same formula: E = V × Q. Multiply the voltage by the charge in coulombs to get the energy in joules. Again, a charge value is required either way.
Why is there no direct joules to volts conversion factor?
Joules measure energy, while volts measure energy per unit of charge. They belong to different physical dimensions and can only be related once a specific amount of charge, in coulombs, is introduced into the calculation.
For working with plain energy units on their own, see the energy unit converter. For other electrical calculations, see the calculator library on the site.