Ohm's Law Calculator

Ohm's Law is evaluated from Voltage, Current and Resistance. The calculation reports Voltage, Current and Resistance.

Results

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About the Ohm's Law Calculator

Ohm's Law is treated here as a quantitative relation between Voltage, Current, Resistance and Power and Voltage, Current, Resistance and Power.

The calculator uses a multi formula configuration. Each reported value is read as a direct evaluation of the stored rules with the declared field formats and units.

Formula basis:
Ohm's Law triangle: V = I x R → I = V/R → R = V/I
Watt's Law: P = V x I
Combined: P = I^2 x R = V^2 / R
Solving for unknowns (any 2 inputs → 4 outputs):
Given V, I → R = V/I, P = V x I
Given V, R → I = V/R, P = V^2/R
Given I, R → V = I x R, P = I^2 x R
Given V, P → I = P/V, R = V^2/P
Given I, P → V = P/I, R = P/I^2
Given R, P → V = sqrt(P x R), I = sqrt(P/R)

Interpret the outputs in the order shown by the result fields. Optional inputs affect only the outputs that depend on those variables.

Formula & How It Works

The calculation applies the following relations exactly as recorded in the metadata:

Ohm's Law triangle: V = I x R → I = V/R → R = V/I
Watt's Law: P = V x I
Combined: P = I^2 x R = V^2 / R
Solving for unknowns (any 2 inputs → 4 outputs):
Given V, I → R = V/I, P = V x I
Given V, R → I = V/R, P = V^2/R
Given I, R → V = I x R, P = I^2 x R
Given V, P → I = P/V, R = V^2/P
Given I, P → V = P/I, R = P/I^2
Given R, P → V = sqrt(P x R), I = sqrt(P/R)

Each output field is produced by substituting the supplied inputs into the relevant relation and then applying the declared rounding or text format.

Worked Examples

Example 1: LED Current-Limiting Resistor

Inputs

voltage: 5 current: 0.02

With Voltage = 5 and Current = 0.02 as the stated inputs, the result is the stated variables. Each value corresponds to the declared output fields.

Example 2: Home Appliance Current Draw

Inputs

voltage: 230 power: 1500

With Voltage = 230 and Power = 1,500 as the stated inputs, the result is the stated variables. Each value corresponds to the declared output fields.

Example 3: Battery Circuit Design

Inputs

voltage: 12 resistance: 470

With Voltage = 12 and Resistance = 470 as the stated inputs, the result is the stated variables. Each value corresponds to the declared output fields.

Example 4: Checking Speaker Impedance

Inputs

current: 2 resistance: 8

Voltage: 16 V. Current: 2 A. Resistance: 8 Ω. Power: 32 W

With Current = 2 and Resistance = 8 as the stated inputs, the result is Voltage = 16 V, Current = 2 A and Resistance = 8 Ω. Each value corresponds to the declared output fields.

Common Use Cases

Find missing circuit values when designing electronics
Verify LED resistor values
Calculate power dissipation in a resistor