Calculate voltage, charge, or energy from the other two values using E = V × Q with volts, coulombs, and joules in any unit, plus unit conversion.
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Energy Charge Voltage Formula
The relationship between electrical energy, charge, and voltage is:
E = V*Q
The calculator can also rearrange the same formula to solve for voltage or charge:
V = E/Q
Q = E/V
- E = energy in joules (J)
- V = voltage or electric potential difference in volts (V)
- Q = electric charge in coulombs (C)
Enter any two values and leave the unknown value blank. If you enter voltage and charge, the calculator finds energy. If you enter energy and charge, it finds voltage. If you enter energy and voltage, it finds charge.
The calculator converts all entered values to base SI units before applying the formula: volts, coulombs, and joules. It then converts the result back to the unit selected for the missing value.
Common Unit Conversions for Voltage, Charge, and Energy
Use these conversions to check how the calculator handles different units.
| Quantity | Unit | Equivalent base unit |
|---|---|---|
| Voltage | 1 kV | 1,000 V |
| Voltage | 1 MV | 1,000,000 V |
| Charge | 1 mC | 0.001 C |
| Charge | 1 μC | 0.000001 C |
| Energy | 1 kJ | 1,000 J |
| Energy | 1 MJ | 1,000,000 J |
Example Calculations
Example 1: Calculate energy
You have a voltage of 12 V and a charge of 3 C.
E = V*Q
E = 12*3 = 36 J
The energy is 36 J.
Example 2: Calculate voltage
You have an energy of 2 kJ and a charge of 5 C.
First convert 2 kJ to joules:
2 kJ = 2000 J
Then divide energy by charge:
V = E/Q
V = 2000/5 = 400 V
The voltage is 400 V.
FAQ
What does 1 volt mean in terms of energy and charge?
One volt means one joule of energy is transferred per coulomb of charge. In formula form, 1 V = 1 J/C. For example, if 1 C of charge moves through a potential difference of 1 V, the energy transferred is 1 J.
Can charge or voltage be zero?
If you are solving for voltage using V = E/Q, charge cannot be zero because division by zero is undefined. If you are solving for charge using Q = E/V, voltage cannot be zero for the same reason. If voltage or charge is zero in the energy formula E = V × Q, the calculated energy is zero.
Why are units converted before calculating?
The formula E = V × Q works directly with joules, volts, and coulombs. If you enter kV, mC, μC, kJ, or MJ, the values must be converted to base units first so the result is consistent. After the calculation, the result can be converted back to your selected output unit.
