Electrical Calculations: Ohm's Law and Circuits Explained
The everyday electrical maths every hobbyist and electrician uses — Ohm's law, power, sizing a resistor, combining resistors, and the basics of current, voltage and safe wiring.
Ohm's Law Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Resistance (R)
6.000
- Power (P)
- 24.000
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Ohm's Law Calculator
The Ohm's Law Calculator works out your resistance (r), along with 1 related figure in an instant. Enter voltage (v) and current (i) and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the voltage (v).
- Enter the current (i).
- Read off your resistance (r), together with power (p) — the calculator updates automatically, with no button to press.
Formula
The Ohm's Law Calculator uses the formula:
Resistance (R) = Voltage (V) ÷ Current (I)
Worked example
For example, with voltage (v) of 12 V and current (i) of 2 A, the resistance (r) is 6.000.
| Voltage (V) | 12 V |
|---|---|
| Current (I) | 2 A |
| Resistance (R) | 6.000 |
|---|---|
| Power (P) | 24.000 |
Results are estimates for educational use, not professional advice.
Frequently asked questions
Ohm's law states that voltage equals current times resistance: V = I × R. Rearranged, resistance is V ÷ I. With 12 V and 2 A, resistance is 6 ohms.
Power equals voltage times current: P = V × I. At 12 V and 2 A the power is 24 watts.
Voltage is in volts (V), current in amperes (A), resistance in ohms (Ω) and power in watts (W).
Yes, using the same law: current is V ÷ R and voltage is I × R. This tool solves for resistance and power from voltage and current.
The Ohm's Law Calculator uses the formula: Resistance (R) = Voltage (V) ÷ Current (I). For example, with voltage (v) of 12 V and current (i) of 2 A, the resistance (r) is 6.000.
Enter the voltage (v). Enter the current (i). Read off your resistance (r), together with power (p) — the calculator updates automatically, with no button to press.
Related guides
Ohm's Law Table: Resistance (R) by Voltage (V)
Reference table of resistance (r) for Ohm's Law across a range of voltage (v) values — exact, engine-computed figures you can read off at a glance.
How to Calculate Ohm's Law: Formula, Steps & Examples
Learn how to calculate Ohm's Law — the formula explained step by step, with worked examples and a free calculator to check your answer.