About

In electrical circuits, Voltage (V) is the potential difference that drives current through a resistive load. Whether diagnosing a car battery issue or designing a PCB, knowing the correct voltage is critical to prevent component burnout. This tool simplifies Ohm's Law by allowing you to input any two known variables - Current (I), Resistance (R), or Power (P) - to solve for Voltage.

Unlike standard calculators, this interface adapts to your available data, hiding irrelevant fields to reduce cognitive load. It fully supports metric prefixes, meaning you can input 20mA directly without converting to 0.02A manually, reducing decimal point errors that lead to short circuits.

Formulas

The relationship between Voltage, Current, and Resistance is defined by Ohm's Law:

V = I ⋅ R

When Power is known, the derived formula from Joule's Law is used:

P = V ⋅ I &implies; V = PI

Reference Data

Variable	Symbol	Unit	Solve for V (Formulas)
Voltage	V or E	Volts (V)	Target Result
Current	I	Amperes (A)	V = I × R
Resistance	R	Ohms (Ω)	V = √P × R
Power	P	Watts (W)	V = P ÷ I

Frequently Asked Questions

The Magic Triangle is a visual mnemonic used to remember Ohm's Law. Voltage (V) is at the top, while Current (I) and Resistance (R) are at the bottom. To find a missing value, you cover it up: Cover V, and you see I next to R (multiplication). Cover I, and you see V over R (division).

This calculator is designed for DC (Direct Current) circuits or purely resistive AC circuits. For AC circuits involving capacitors or inductors, you must use Impedance (Z) instead of Resistance (R), and consider phase angles.

If Resistance is zero, it represents a "short circuit". Mathematically, this would imply zero Voltage drop if Current is finite, or infinite Current if Voltage is non-zero. The calculator will return 0V or an error depending on the context.