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Ohm's Law Calculator (Voltage, Current, Resistance, Power)

Given any two of voltage, current, resistance and power, what are the other two?

Single calculationv1.0.0Verified 2026-11-01Runs in your browser

Spec sheet

ohm_power · v1.0.0

Method

V = I·R and P = V·I

01V = I · R
02P = V · I = I² · R = V² / R

Limits — read before relying on it

DC or purely resistive AC; reactive loads need power factor (see the three-phase power calculator).

Sources

Ohm's law and Joule's lawtextbook

Worked example

computed by the same formula

12 V across 6 Ω

Inputs

Known values: Voltage & resistance
First value (V, A or W — in the order above): 12
Second value (V, A or Ω — in the order above): 6

Result

Voltage: 12 V
Current: 2 A
Resistance: 6 Ω
Power: 24 W

Questions

How is the ohm's law calculator calculated?

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V = I·R and P = V·I. V = I · R · P = V · I = I² · R = V² / R

Example: 12 V across 6 Ω?

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Voltage: 12 V; current: 2 A.

What does this calculator not cover?

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DC or purely resistive AC; reactive loads need power factor (see the three-phase power calculator).

Where do the numbers come from?

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Sources: Ohm's law and Joule's law. The formula is versioned (ohm_power v1.0.0) and covered by automated tests.

Is my data stored?

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No. The calculation runs in your browser and nothing is sent unless you choose to save a shareable link.

Also searched asohms law calculator · voltage current resistance · calculate amps from watts · watts to amps · resistance calculator · power calculator watts

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Three-Phase Power Calculator (kW ↔ Amps)

How many amps does a three-phase (or single-phase) load draw — or how many kW is a given current?

P = √3 · V · I · PF