Ohm's Law Resistance Calculator: Calculate Resistance, Voltage & Current (V = I × R)

Ohm's Law is one of the most fundamental principles in electrical engineering and electronics, describing the relationship between voltage, current, and resistance in electrical circuits. Understanding Ohm's Law is essential for designing circuits, troubleshooting electrical systems, and working with any electronic device. Our Ohm's Law Resistance Calculator simplifies these calculations, allowing you to determine resistance, voltage, or current using the relationship: V = I × R.

Named after German physicist Georg Simon Ohm, this law states that the current through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them. This simple yet powerful equation is the cornerstone of electrical circuit analysis and applies to countless real-world applications, from simple light bulbs to complex electronic systems.

Our Ohm's Law Resistance Calculator offers three calculation modes:

1. Calculate Resistance (R): Enter voltage (V) and current (I). The calculator determines the resistance using R = V/I.
2. Calculate Voltage (V): Enter current (I) and resistance (R). The calculator determines the voltage using V = I × R.
3. Calculate Current (I): Enter voltage (V) and resistance (R). The calculator determines the current using I = V/R.

Select your calculation mode, enter the known values with your preferred units, and click Calculate to get instant results with detailed step-by-step solutions. The calculator supports multiple units for voltage (V, mV, kV, μV), current (A, mA, μA, kA, nA), and resistance (Ω, kΩ, MΩ, mΩ, μΩ).

The fundamental formula for Ohm's Law is:

Components of Ohm's Law:

• Voltage (V): The electrical potential difference between two points, measured in Volts (V). Voltage is the "pressure" that pushes electric charges through a circuit. Common units include volts (V), millivolts (mV), and kilovolts (kV).
• Current (I): The flow of electric charge through a conductor, measured in Amperes (A). Current represents the rate at which charge flows. One ampere equals one coulomb per second. Common units include amperes (A), milliamperes (mA), and microamperes (μA).
• Resistance (R): The opposition to the flow of electric current, measured in Ohms (Ω). Resistance determines how much current will flow for a given voltage. One ohm equals one volt per ampere. Common units include ohms (Ω), kiloohms (kΩ), and megaohms (MΩ).

Rearranging Ohm's Law:

You can rearrange Ohm's Law to solve for any variable:

• Voltage: V = I × R
• Current: I = V / R
• Resistance: R = V / I

Physical Interpretation:

Ohm's Law shows that voltage and current are directly proportional when resistance is constant: doubling the voltage doubles the current. Conversely, current and resistance are inversely proportional when voltage is constant: doubling the resistance halves the current. This linear relationship holds for most conductors at constant temperature, making it invaluable for circuit analysis and design.

Ohm's Law calculations are essential in numerous applications:

• Circuit Design: Calculating component values, selecting appropriate resistors, and designing voltage dividers, current limiters, and bias circuits.
• Electronic Troubleshooting: Diagnosing circuit problems, verifying component values, and understanding circuit behavior in electronic devices.
• Power Supply Design: Calculating voltage drops, current requirements, and resistance values for power supply circuits and voltage regulators.
• Electrical Safety: Understanding current flow to ensure safe circuit design, proper fuse sizing, and protection device selection.
• LED Circuits: Calculating current-limiting resistor values for LEDs to prevent damage and ensure proper operation.
• Sensor Circuits: Designing signal conditioning circuits, calculating sensor output voltages, and determining appropriate pull-up or pull-down resistors.
• Audio Electronics: Designing amplifier circuits, calculating gain, and understanding impedance matching.
• Education and Training: Teaching electrical engineering principles, circuit analysis techniques, and fundamental electronics concepts.

Resistors come in standard values and serve various purposes:

Electrical power is closely related to Ohm's Law:

Power represents the rate at which electrical energy is converted to other forms (such as heat or light). By combining Ohm's Law with power calculations, you can determine energy consumption, heat generation, and component ratings in electrical circuits.

While Ohm's Law is fundamental, it has important limitations:

• Ohmic vs. Non-Ohmic Devices: Ohm's Law applies to "ohmic" materials where resistance is constant. Non-ohmic devices (diodes, transistors, LEDs) don't follow Ohm's Law due to non-linear resistance.
• Temperature Dependence: Resistance changes with temperature. Most conductors increase resistance with temperature (positive temperature coefficient), while some materials decrease resistance (negative temperature coefficient).
• AC Circuits: In alternating current (AC) circuits, impedance (which includes resistance, capacitive reactance, and inductive reactance) replaces simple resistance.
• Frequency Dependence: At high frequencies, circuit behavior is affected by parasitic capacitance and inductance, requiring more complex analysis beyond simple Ohm's Law.
• Voltage and Current Ranges: Ohm's Law applies over limited voltage and current ranges. Very high voltages or currents may cause breakdown, heating effects, or other non-linear behaviors.

Ohm's Law is the foundation of electrical circuit analysis, providing the essential relationship between voltage, current, and resistance. Our Ohm's Law Resistance Calculator provides a powerful and accurate tool for determining resistance, voltage, or current using the relationship V = I × R.

By simplifying calculations and offering comprehensive unit support with detailed step-by-step solutions, this calculator empowers engineers, students, and electronics enthusiasts to analyze circuits effectively. For related calculations, explore our Capacitance Calculator for capacitor calculations or our Parallel Resistor Calculator for resistor network analysis.