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Ohm's Law Calculator

Calculate voltage, current, resistance, or power instantly with a focused Ohm's Law calculator for electricians, students, and DIY wiring checks.

Use calculator Open circuit simulator
Professional workflow

Enter any two known values and get the missing electrical value instantly.

V = I × R · P = V × I · P = I² × R
  • Fast calculator for the relationships technicians use every day: volts, amps, ohms, and watts.
  • Useful for checking expected meter readings before troubleshooting a circuit.
  • Keeps formulas visible so students understand the result instead of only copying a number.

Calculate voltage, current, or resistance using V = IR

💡 Tip: Enter any 2 values, leave the 3rd empty to calculate it

Leave exactly one value blank when you want the calculator to solve it.
If all three measured values are entered, use the validation result to catch inconsistent readings.
Check units before comparing measured values from a real circuit.

V = I × R

Voltage = Current × Resistance

Inputs to prepare
  • Any two known values
  • Voltage in volts
  • Current in amps
  • Resistance in ohms
  • Power in watts when available
Worked example

Example: Find current from voltage and resistance

Given
  • • Voltage = 120 V
  • • Resistance = 60 Ω
Steps
  1. 1. Use I = V / R.
  2. 2. Divide 120 by 60.
I = 2 A, and the load power is P = 120 V × 2 A = 240 W.
Common use cases
  • Electrician exam practice
  • Checking expected current from a known load
  • Understanding resistance or wattage changes in simple circuits
How to read results
  • Very high current for a low resistance can indicate a short-circuit risk.
  • Power result helps estimate heat and equipment loading.
  • For AC circuits with motors or transformers, consider power factor and impedance separately.
Code and safety notes
  • Ohm’s Law is a base electrical relationship, not a code compliance check.
  • Real loads may be non-linear, inductive, temperature-dependent, or controlled electronically.
  • Always confirm live circuits with proper instruments and safe work practices.

Frequently asked questions

What is Ohm's Law?

Ohm's Law describes the relationship between voltage, current, and resistance: V = I × R.

Which values do I need to enter?

Enter any two known values, such as voltage and resistance, and the calculator solves the remaining value.

Can I use this for exam practice?

Yes. It is designed for quick repetition while studying electrical calculations.

Can I use this for real wiring work?

Use it as a reference only. Real installations must follow local code and be checked by a qualified electrician.