About this calculator
Ohm's law is one of the most fundamental laws in electricity, describing the relationship between voltage, current, and resistance. The formula for Ohm's law is: V = I × R, where V is voltage (volts), I is current (amps), and R is resistance (ohms). Ohm's law is widely used in circuit analysis, electrical design, troubleshooting and other fields. Our free online Ohm's Law calculator provides a simple, fast, and accurate solution.
The Ohm's Law calculator can calculate a third quantity from two known quantities. For example, given a voltage of 12V and a resistance of 4Ω, the current I = V / R = 12V / 4Ω = 3A can be calculated. Knowing the current 2A and the resistance 5Ω, we can calculate the voltage V = I × R = 2A × 5Ω = 10V.
Using the Ohm's Law Calculator is easy and intuitive. Select the quantity you want to calculate (voltage, current or resistance), enter two known quantities, click the Calculate button and get the results instantly. This tool is especially useful for students, electricians, electronics enthusiasts and anyone who needs to perform circuit calculations.
What it calculates
The Ohm's law calculator solves unknown voltage, current, or resistance from their relationship and can help with electrical power.
Formula
- V = I * R.
- I = V / R.
- R = V / I.
- P = V * I.
Inputs
- Any two known values: voltage V, current I, resistance R.
- Optional values for power calculations.
Example
| Input | Formula | Result |
|---|---|---|
| I=2 A, R=6 ohm | V=IR | 12 V |
| V=12 V, R=4 ohm | I=V/R | 3 A |
| V=10 V, I=2 A | R=V/I | 5 ohm |
How to interpret the result
Voltage pushes current through resistance. Higher resistance gives lower current at the same voltage; power is the rate of energy conversion.
Common mistakes
- Use consistent units: V, A, and ohm.
- Do not divide by zero resistance.
- Real circuits may vary with temperature and component behavior.
How to use
Using the Ohm's Law calculator is easy. First, select the target to calculate: calculate voltage (V), calculate current (I), or calculate resistance (R).
If calculating voltage, enter the current (amps A) and resistance (ohms Ω). For example, the current is 2A, the resistance is 5Ω, click Calculate, the result is: voltage = 10V.
If you are calculating current, enter the voltage (volts V) and resistance (ohms Ω). For example, the voltage is 12V, the resistance is 4Ω, click Calculate, the result is: current = 3A.
If you are calculating resistance, enter the voltage (Volts V) and current (Amperes A). For example, the voltage is 9V, the current is 0.5A, click Calculate, the result is: resistance = 18Ω. Click the "Reset" button to clear all inputs and start a new calculation.
Main features
This Ohm's Law calculator has the following features: supports calculation of any one of voltage, current, and resistance; uses standard Ohm's Law formulas; automatically detects invalid inputs (dividing by zero, etc.); displays calculation formulas; has a simple and intuitive interface, easy to use; has fast response speed, and calculation results are displayed immediately; completely free, no registration or download required; supports desktop and mobile device access; suitable for student learning and electrician practice.
Use cases
The Ohm's Law calculator is useful in several scenarios. When students study electricity, they can use it to verify Ohm's law and complete physics homework. For example, calculate voltage, current and resistance in series circuits, parallel circuits.
It can be used by electricians to diagnose faults when repairing electrical appliances. For example, measure voltage and current, calculate resistance, and determine whether a component is damaged. Electronics enthusiasts can use it to select appropriate components when designing circuits. For example, if the supply voltage and LED operating current are known, calculate the required current limiting resistor.
In the laboratory, it can be used to analyze experimental data. For example, measuring current at different voltages to verify Ohm's law. In teaching, it can be used to demonstrate the relationship between voltage, current, and resistance. Whether studying, working or experimenting, the Ohm's Law Calculator is a useful tool.