Ohm's Law states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance: V = I × R.

Voltage in Volts (V), Current in Amperes (A), Resistance in Ohms (Ω), and Power in Watts (W).

Does Ohm's Law apply to AC circuits?

Ohm's Law applies directly to resistive AC circuits. For circuits with capacitors or inductors, impedance (Z) replaces resistance.

Can I use milliamps or kilohms?

Enter all values in base units (amps, ohms, volts). Convert first: 50 mA = 0.05 A, 4.7 kΩ = 4700 Ω.

What if resistance is zero?

Zero resistance means a short circuit — current would theoretically be infinite. The calculator will flag this as an invalid input.

Everyday

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Ohms Law Calculator - Voltage Current Resistance Online

Solve for voltage, current, resistance, or power given any two electrical values using Ohm's Law.

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How to use this calculator

👉 Fill in the boxes below and your answer appears instantly — no maths needed, we do it all for you! 🎉

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In plain English — what does this do?

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📌 Direct Answer & Summary

The Ohm's Law Calculator solves for any one of the four fundamental electrical quantities — Voltage (V), Current (I), Resistance (R), and Power (P) — when you provide any two of them. It uses the relationships V = I × R and P = V × I.

Select two known values and enter them below.

Known Value 1

Known Value 2

What is Ohms Law Calculator - Voltage Current Resistance Online?

How to use it

1️⃣ Select the two values you already know from the first two dropdowns.
2️⃣ Enter the numeric values for those two quantities.
3️⃣ Click Calculate to solve for all four values.
4️⃣ The results show Voltage (V), Current (A), Resistance (Ω), and Power (W).
5️⃣ Use this for circuit design, troubleshooting, or selecting fuses and wire gauges.

Formula

V = I × R. I = V / R. R = V / I. P = V × I = I² × R = V² / R.

💡 See it in action — a real example

Know voltage (12 V) and resistance (6 Ω): I = 12 / 6 = 2 A. P = 12 × 2 = 24 W.

❓ Common questions

What is Ohm's Law?: Ohm's Law states that the current through a conductor is directly proportional to the voltage across it and inversely proportional to its resistance: V = I × R.
What units are used?: Voltage in Volts (V), Current in Amperes (A), Resistance in Ohms (Ω), and Power in Watts (W).
Does Ohm's Law apply to AC circuits?: Ohm's Law applies directly to resistive AC circuits. For circuits with capacitors or inductors, impedance (Z) replaces resistance.
Can I use milliamps or kilohms?: Enter all values in base units (amps, ohms, volts). Convert first: 50 mA = 0.05 A, 4.7 kΩ = 4700 Ω.
What if resistance is zero?: Zero resistance means a short circuit — current would theoretically be infinite. The calculator will flag this as an invalid input.

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