Ohm's Law Calculator - Voltage, Current, Resistance & Power Solver

Ohm's Law & Power Calculator

Enter any two known values to calculate Voltage, Current, Resistance, and Power.

Voltage (V in Volts):

Current (I in Amperes):

Resistance (R in Ohms Ω):

Power (P in Watts):

Voltage (V)

0.00 V

Current (I)

0.00 A

Resistance (R)

0.00 Ω

Electric Power (P)

0.00 W

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Ohm's Law Calculator: Calculate Voltage, Current, Resistance & Power

Ohm's Law is one of the most foundational principles in physics and electrical engineering. Formulated by German physicist Georg Ohm, it defines the mathematical relationship between electrical potential difference (voltage), electric current flow, and material resistance.

Our Ohm's Law Calculator allows students, electrical technicians, and electronics hobbyists to determine any two missing electrical parameters simply by entering two known values.

The Core Formulas of Ohm's Law and Electric Power

Depending on which values you have available, the following standard equations govern direct current (DC) circuits:

Variable to Find	Standard Formula	Unit of Measurement
Voltage (V)	V = I × R or V = P ÷ I	Volts (V)
Current (I)	I = V ÷ R or I = P ÷ V	Amperes (A)
Resistance (R)	R = V ÷ I or R = V² ÷ P	Ohms (Ω)
Power (P)	P = V × I or P = I² × R	Watts (W)

The Ohm's Law Pie Chart Relationship

Key Formulas Summary:
• Voltage: $V = \sqrt{P \times R}$
• Current: $I = \sqrt{P \div R}$
• Power: $P = \frac{V^2}{R} = I^2 \times R = V \times I$

Practical Applications of Ohm's Law

• Sizing Electrical Wires: Calculate current flow to prevent overheating and ensure safety compliance.
• Resistor Sizing in Circuits: Determine the exact resistance needed to protect LEDs and microcontrollers from over-voltage.
• Power Consumption Estimation: Calculate power in Watts to understand household energy usage and battery drain rates.

Frequently Asked Questions (FAQs)

What are the limitations of Ohm's Law?

Ohm's Law only applies to ohmic conductors at a constant temperature. It does not apply to non-linear components such as diodes, transistors, or vacuum tubes.

What is the relationship between power and resistance?

If voltage remains constant, increasing resistance decreases power consumption ($P = V^2 / R$). If current remains constant, increasing resistance increases power consumption ($P = I^2 \times R$).

Can this calculator be used for AC circuits?

Yes, for purely resistive AC circuits. For circuits with inductors or capacitors, impedance (Z) must be used instead of simple DC resistance (R).