Ohms Law Calculator
Calculate Voltage, Current, Resistance, and Power instantly using our Ohms Law calculator. Simply enter any two known values, and we'll compute the other two for you. This essential tool is perfect for electronics students, engineers, and DIY enthusiasts. Explore more tools on free science and engineering calculators on CalculatorBolt.
Calculator Inputs
Preset Examples
Ohm's Law Wheel
The Ohm's Law wheel shows all possible formulas to calculate V, I, R, and P. Cover the value you want to find, and the remaining values show the formula.
Unit Conversion Reference
| Quantity | Symbol | Units |
|---|---|---|
| Voltage | V | Volts (V), kilovolts (kV), millivolts (mV), microvolts (µV) |
| Current | I | Amperes (A), kiloamperes (kA), milliamperes (mA), microamperes (µA) |
| Resistance | R | Ohms (Ω), kilohms (kΩ), megohms (MΩ) |
| Power | P | Watts (W), kilowatts (kW), milliwatts (mW) |
How it works
Ohm's Law defines the fundamental relationship between Voltage (V), Current (I), and Resistance (R) in an electrical circuit: V = I × R. Power (P) is the rate at which energy is used and is related to these values by the formula P = V × I. By knowing any two of these four values, you can calculate the other two.
Inputs explained
- Voltage (V): The electrical potential difference, measured in Volts (V). Think of it as the pressure in a water pipe.
- Current (I): The flow of electric charge, measured in Amperes (A). Think of it as the flow rate of the water.
- Resistance (R): The opposition to the flow of current, measured in Ohms (Ω). Think of it as the narrowness of the pipe.
- Power (P): The rate of energy consumption or production, measured in Watts (W).
Example
You want to find the current drawn by a 60-watt light bulb connected to a standard 120-volt power supply.
- Enter Voltage (V): 120
- Enter Power (P): 60
- Click Calculate.
The calculator will determine the Current (I) is 0.5 Amps and the Resistance (R) is 240 Ohms.
Tips & notes
- Always ensure you are using the correct units. The calculator handles common prefixes like kilo (k) and milli (m), but the base formulas use Volts, Amps, Ohms, and Watts.
- This calculator is for DC circuits. For AC circuits, impedance and power factor also need to be considered.
- Never work on live electrical circuits. Always ensure power is disconnected before making any physical changes.
FAQs
Disclaimer
This calculator provides results based on standard electrical formulas. It is intended for educational and informational purposes. Always consult a qualified electrician and adhere to all safety precautions when working with electrical systems.