What formula does this calculator use?

The calculator uses E(J) = V(V) × Q(C). Voltage (V) is the potential difference in volts and Q is the electric charge in coulombs. One joule equals one volt times one coulomb (1 J = 1 V · C).

A coulomb (C) is the SI unit of electric charge. One coulomb equals the charge transported by a current of one ampere in one second (1 C = 1 A · s). For example, 2–3 ampere-hours equals 7,200–10,800 coulombs.

How is this different from E = I × V × t?

For constant voltage and current they are equivalent. Charge Q = I × t, so E = V × Q = V × I × t. If voltage or current changes over time, energy must instead be integrated over the actual waveform.

Can I calculate capacitor energy with this tool?

Not directly from the displayed V × Q result. An ideal capacitor charged from zero stores E = ½ × C × V² = ½ × V × Q because its voltage rises from zero to V. For capacitor stored energy, divide this tool’s V × Q result by two when Q = C × V.

A joule (J) is the SI unit of energy and work. One joule equals one newton-meter, one watt-second, or one volt-coulomb. It is also the energy dissipated as heat when one ampere flows through one ohm for one second.

What are the other energy units shown?

The result panel also displays kilojoules (1 kJ = 1,000 J), watt-hours (1 Wh = 3,600 J), and millijoules (1 mJ = 0.001 J) for convenience when working with very small or very large energy values.

Volts to Joules Calculator

Enter voltage in volts and charge in coulombs to calculate energy in joules using E = V × Q.

Input Parameters

Voltage (V)

Charge (C)

Result

Enter values and press Calculate

Formula Reference

Energy

E (J) = V (V) × Q (C)

Charge

Q (C) = I (A) × t (s)

Unit Check

1 J = 1 V × 1 C

Result copied!

Summary

Enter voltage in volts and charge in coulombs to calculate energy in joules using E = V × Q.

How it works

Enter the voltage in volts (V).
Enter the electric charge in coulombs (C).
Click Calculate to apply the formula E = V × Q.
The result is displayed in joules (J) along with kilojoules and watt-hours.
Use the Reset button to clear all fields and start over.

Use cases

Determine idealized energy delivered at a constant battery terminal voltage from charge drawn.
Calculate work done moving charge through a fixed potential difference.
Estimate work done moving a charge through a potential difference in circuit design.
Convert charge-voltage product to joules for physics homework and exams.
Analyze energy in charged particle accelerators.
Check energy balance in electrochemical cell reactions.

Frequently Asked Questions

Last updated: 2026-09-19 · Reviewed by Nham Vu