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Mihsaba›Ohm’s Law Calculator

Ohm’s Law Calculator

Enter any two of voltage, current, resistance and power to solve the other two, with common milli, micro, kilo and mega unit prefixes.

How to use

This calculator combines Ohm’s law V=IR with the power relationships. Enter exactly two values among voltage, current, resistance and power, select their units, and the calculator normalizes to V, A, Ω and W before solving the other two.

  1. Fill exactly two fields and leave the other two blank.
  2. Choose the unit for each known value, such as mA or kΩ.
  3. Calculate to display V, I, R and P together in base SI units.

How it is calculated

V = I×R; P = V×I = I²R = V²÷R

Example

Example: 12 V and 4 Ω produce I=3 A and P=36 W. Using 500 mA and 24 Ω produces 12 V and 6 W after the calculator normalizes 500 mA to 0.5 A.

Important notes

The model assumes an ideal ohmic element using non-negative magnitudes in DC or a purely resistive case. In reactive AC circuits or when power factor is not 1, resistance becomes impedance and P=VI is not generally real power. Underdetermined zero pairs such as V=0 and I=0 are rejected rather than inventing a resistance.

Frequently asked questions

Do I need to convert mA to A manually?

No. Select mA and the calculator normalizes it internally.

Can I enter resistance and power only?

Yes. For an ideal resistor it solves I = √(P/R) and then V = IR.

Does this work for motors and general AC circuits?

Not by itself. Reactive AC cases may require impedance, phase and power factor.

Is this calculator free?

Yes. It is free to use and requires no account.