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Ohm’s Law Calculator

Solve voltage, current, resistance and power for an ideal steady-state DC resistor.

Your numbers

Make it your own
Updates as you type
Voltage
12V

Calculated from your inputs · rounded for display

Current2A
Resistance6Ω
Power24W

Positive steady-state DC values for an ideal resistive load. Not an AC impedance, wire-sizing or electrical-safety assessment.

Your calculation, step by step

No black boxes
  1. Known pair: VI.
  2. Ohm’s law: V = I × R.
  3. Resistive power: P = V × I = I²R = V²/R.
  4. V = 12 V; I = 2 A; R = 6 Ω; P = 24 W.

How to use this calculator

  1. Enter your own values in the labeled fields. Check the units and assumptions before comparing results. Only the fields needed for your selected calculation mode are shown.
  2. Your answer updates automatically. Review the calculation steps to see exactly how it was calculated.
  3. Copy, share, save, or download your result. Saved inputs stay on this device.

How the calculation works

V = I × R; P = V × I = I²R = V²/R

Choose the two positive known quantities; the remaining quantities follow from Ohm’s law and resistive power identities. Units are volts, amperes, ohms and watts. The model assumes a steady-state DC ideal resistor and does not handle AC phase, impedance, transient behavior or component safety ratings.

A worked example

At 12 V and 2 A, resistance is 12 ÷ 2 = 6 Ω and power is 12 × 2 = 24 W.

Reading your result

Use the main result together with its units and supporting figures. Display values are rounded; calculations keep their underlying precision. A change in inputs or assumptions can change the answer. Compare the step-by-step working with your intended use before relying on an estimate.

Frequently asked questions

Does this handle AC circuits?

No. Reactive impedance and power factor are not included.

Can it choose a safe resistor or wire?

No. Thermal ratings and installation requirements need separate assessment.

Sources & methodology

This calculator uses the mathematical identity and assumptions stated above. No current rates, prices, or external data are loaded. Conversion tools use international unit definitions.

Formula review: October 24, 2026. Read our methodology.