Ohm's Law Calculator
Calculate voltage, current, resistance using V = IR
About the Ohm's Law Calculator
Ohm's Law is the fundamental relationship in electrical circuits: voltage equals current times resistance (V = IR). The Ohm's Law Calculator solves for any of these three variables when you know the other two, supporting multiple unit systems for voltage (V, mV, kV), current (A, mA, kA), and resistance (Ω, kΩ, MΩ). It also calculates power automatically using P = VI.
Students solve electronics homework problems, electricians design and troubleshoot circuits, and engineers calculate component values for PCB design. The calculator handles unit conversions automatically and displays results in multiple units simultaneously for easy comparison.
Because calculations run entirely in your browser using JavaScript, you can solve circuit problems without any data leaving your device. The tool clearly explains the relationship between voltage, current, resistance, and power in the FAQ section.
How to Use the Ohm's Law Calculator
- Select what you want to calculate from the dropdown: voltage, current, or resistance.
- Fill in the two electrical quantities you know, such as the supply voltage and the resistance.
- Match each input to its unit — volts, millivolts, or kilovolts; amps or milliamps; ohms, kilohms, or megohms.
- Click Calculate to solve for the unknown variable using V = IR.
- View the result plus the calculated power (P = VI) displayed in multiple units for convenience.
Why Use ToolForge’s Ohm's Law Calculator
- Circuit calculations run locally in your browser—no data is sent to any server, and the tool works offline for secure, private electrical design work.
- Solves for any of the three variables (voltage, current, resistance) when you know the other two, and automatically calculates power as a bonus.
- Handles electrical unit conversions automatically, working with volts/millivolts/kilovolts, amps/milliamps/kiloamps, and ohms/kiloohms/megaohms.
- Displays voltage, current, resistance, and power in multiple units at once, covering the conventions used in different regions and industries.
Frequently Asked Questions
What is Ohm's Law?
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points, expressed as V = IR, where V is voltage, I is current, and R is resistance. This fundamental relationship underlies all DC circuit analysis.
Which voltage, current, and resistance units are supported?
The calculator supports volts, millivolts, and kilovolts for voltage; amperes, milliamperes, and kiloamperes for current; and ohms, kilohms, and megohms for resistance. Power is calculated and displayed in watts.
Can I calculate power as well?
Yes, the calculator automatically calculates power (P = VI) along with voltage, current, and resistance. Power tells you how much energy the circuit consumes or delivers, measured in watts.
What are the practical applications of Ohm's Law?
Ohm's Law is used extensively in electronics for circuit design, troubleshooting, and analysis. It helps calculate component values like resistors, determine current flow through branches, and ensure safe operating conditions by preventing excessive current.
What is the relationship between power and Ohm's Law?
Power can be calculated using P = VI (power equals voltage times current). Using Ohm's Law to substitute V = IR, you can also express power as P = I²R or P = V²/R. These alternative forms are useful when you know different combinations of variables.
