Ohm's Law Calculator

What is the Ohm's Law Calculator?

Ohm's Law is the most used equation in basic electronics. It describes the relationship between voltage, current, and resistance in a circuit, and knowing any two of those values tells you the third. This calculator is useful for electronics students, hobbyists building circuits, and anyone doing electrical work who doesn't want to do the algebra by hand. CalciHub's version handles all three versions of the formula so you can solve for whichever variable you need.

How Does It Work?

The core idea: voltage equals current multiplied by resistance. That's it. Three variables, one equation, three possible arrangements depending on what you're solving for.

V = I × R

I = V / R

R = V / I

• V = Voltage, measured in volts (V)

• I = Current, measured in amperes (A)

• R = Resistance, measured in ohms (Ω)

How to Use CalciHub's Ohm's Law Calculator

1. Select which value you want to calculate: voltage, current, or resistance.

2. Enter the two known values in their respective fields.

3. Click Calculate to get your result instantly.

Tip: Keep your units consistent. If your current is in milliamps (mA), convert to amps (divide by 1000) before entering the value, or your answer will be off.

A Quick Example

An electronics student is testing a resistor. The power supply runs at 9 volts, and the resistor has a 470 ohm rating.

• V = 9 V

• R = 470 Ω

• Solving for I: I = 9 / 470 = 0.01915 A ≈ 19.1 mA

That tells the student the circuit draws about 19 milliamps — useful for checking whether a component is within its rated current range before powering anything up.

Frequently Asked Questions