Which two inputs do I need?

Pick what you solve for, then supply a valid pair (for example voltage+resistance for current, or current+resistance for voltage).

Is this safe for house wiring?

No. Use it for learning and low-voltage electronics context. Household wiring requires code-compliant design and a qualified electrician.

Ohm's Law Calculator

Solve Ohm’s law for voltage, current, resistance, or power from any valid pair of known values—clear DC/resistive relationships for DIY electronics.

Solve any leg of V·I·R

Includes power

Educational DC math

Computes the missing Ohm’s law quantity (V, I, R, or P) from the known inputs you enter.

Limitation: Educational estimate only.

Jump to calculator · Sources & review

Solve forVoltage (V)Current (A)Resistance (Ω)Power (W)

How to Use the Ohm's Law Calculator

Enter the fields below, then review the educational estimate.

Choose which quantity to solve for.

Resistive / DC model

This worksheet uses ideal Ohm’s law. Reactive AC circuits need impedance, not just R.

What This Calculator Estimates

Returns a consistent set of voltage, current, resistance, and power from classic Ohm’s law identities.

Worked Examples

12 V from 2 A through 6 Ω

Inputs

solveFor:voltage

current:2

resistance:6

Result

12 V (24 W)

V = I·R = 2×6 = 12; P = V·I = 24 W.

Current from 120 V across 60 Ω

Inputs

solveFor:current

voltage:120

resistance:60

Result

2 A (240 W)

I = V/R = 120/60 = 2 A; P = 240 W.

Safety first

De-energize circuits before measuring. When in doubt, stop and consult a licensed electrician.

Frequently Asked Questions

Only as a rough resistive estimate. Motors and other inductive loads need power factor and impedance, not DC Ohm’s law alone.

Still have questions about this calculation?

Try the Calculator

Formulas & Assumptions

Transparent educational arithmetic. Not NEC design software or a wiring permit.

Formula

V = I · R or V = P / I

Voltage

V = I · R or V = P / I

Current

I = V / R or I = P / V

Resistance & power

R = V / I; P = V · I = I² · R = V² / R

Scientific Background

Ohm’s law is the linear constitutive relation for an ideal resistor. Real wires also have temperature-dependent resistance; this tool ignores temperature correction.

Sources & review

Ohm's Law Calculator documents the references behind its formulas and assumptions. Always treat results as educational estimates, not personalized professional advice.

Last reviewed

July 22, 2026

Reference
physics.nist.gov
https://physics.nist.gov/cuu/Constants/index.html
Reference
nist.gov
https://www.nist.gov/pml/owm/wire-gauge-and-current-carrying-capacity
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