Ohm’s law & power calculator

Fill in any two of voltage, current, resistance and power — the calculator derives the other two instantly as you type.

Voltage (V)

Current (A)

Resistance (Ω)

Power (W)

Voltage: 12.00V
Current: 2.000A
Resistance: 6.00Ω
Power: 24.00W

P = V × I · P = I² × R · P = V² ÷ R · V = I × R

Spec the interconnect

Once you know the power and current, pick connectors, terminal blocks and high-current connectors rated for the continuous current the circuit will carry.

Frequently asked questions

How do I calculate power from voltage and current?

Electrical power is the product of voltage and current: P = V × I. From resistance it can also be written as P = I² × R or P = V² ÷ R. With the default 12 V and 2 A the calculator resolves 6 Ω and 24 W.

Why does the calculator ask for exactly two values?

Any two of voltage, current, resistance and power determine the other two through V = I × R and P = V × I. Filling three or more fields over-constrains the set, so the tool flags the conflict and asks you to clear one rather than silently picking an arbitrary pair.

How are resistance and current related in a circuit?

Ohm’s law gives V = I × R, so current is voltage divided by resistance and resistance is voltage divided by current. Entering voltage and resistance, for example, yields current as I = V ÷ R and power as P = V² ÷ R.

How it works

The four quantities are linked by V = I × R and P = V × I, which also give P = I² × R and P = V² ÷ R. Two known values are enough to resolve all four — fill three or more and the calculator asks you to clear one.

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