Ohm's Law Calculator
Calculate voltage, current, resistance, and power using Ohm's Law. Enter any two known values and get instant results for the remaining two. Perfect for students, engineers, and electronics enthusiasts.
What Is Ohm's Law?
Ohm's Law is a fundamental principle in electrical engineering that describes the relationship between voltage, current, and resistance in an electrical circuit. It states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points and inversely proportional to the resistance between them.
The law is expressed by the formula:
V = I × R
Where:
V = Voltage (Volts)
I = Current (Amperes)
R = Resistance (Ohms)
Power Formula: P = V × I = I² × R = V² / R
This calculator allows you to solve for any of the four values — voltage, current, resistance, or power — by entering any two known values.
How the Ohm's Law Calculator Works
The calculator uses the following formulas:
- Voltage: V = I × R (when I and R are known)
- Current: I = V / R (when V and R are known)
- Resistance: R = V / I (when V and I are known)
- Power: P = V × I (when V and I are known)
Enter any two values and leave the others blank. The calculator will determine which values are missing and compute them using the appropriate formulas. If you enter three or four values, the calculator will verify consistency and highlight any discrepancies.
Why Use This Ohm's Law Calculator?
- Flexible Input: Enter any two values — the calculator handles the rest.
- Visual Representation: A bar chart shows the relative scale of each value.
- Educational: See the formula and step-by-step calculation breakdown.
- Unit Prefixes: Optionally display values with kilo (k), mega (M), and other prefixes.
- Free & Private: No registration, no data storage.
Understanding Electrical Units
- Volt (V): The unit of electrical potential difference.
- Ampere (A): The unit of electrical current.
- Ohm (Ω): The unit of electrical resistance.
- Watt (W): The unit of electrical power.
❓ Ohm's Law Calculator FAQ
What is Ohm's Law?
Ohm's Law is a fundamental principle in electrical engineering that states the current through a conductor is directly proportional to the voltage across it and inversely proportional to the resistance. The formula is V = I × R.
What are the units used in Ohm's Law?
Voltage is measured in Volts (V), current in Amperes (A), resistance in Ohms (Ω), and power in Watts (W).
How do I calculate voltage using Ohm's Law?
Voltage = Current × Resistance. For example, if current is 2 A and resistance is 6 Ω, voltage = 2 × 6 = 12 V.
How do I calculate current using Ohm's Law?
Current = Voltage ÷ Resistance. For example, if voltage is 12 V and resistance is 6 Ω, current = 12 ÷ 6 = 2 A.
How do I calculate resistance using Ohm's Law?
Resistance = Voltage ÷ Current. For example, if voltage is 12 V and current is 2 A, resistance = 12 ÷ 2 = 6 Ω.
How do I calculate power using Ohm's Law?
Power = Voltage × Current. For example, if voltage is 12 V and current is 2 A, power = 12 × 2 = 24 W.
What is the difference between AC and DC in Ohm's Law?
Ohm's Law applies to both AC and DC circuits, but for AC circuits, impedance (Z) is used instead of resistance (R) when reactive components like capacitors and inductors are present.
What is the difference between resistance and impedance?
Resistance (R) applies to DC circuits and purely resistive AC circuits. Impedance (Z) applies to AC circuits with reactive components and includes both resistance and reactance.
What are common unit prefixes used in electrical calculations?
Common prefixes include: kilo (k) = 1,000, mega (M) = 1,000,000, milli (m) = 0.001, and micro (µ) = 0.000001. This calculator can display values with these prefixes.
How do I convert milliamps to amps?
Divide milliamps by 1,000. For example, 500 mA = 0.5 A. This calculator handles unit conversions automatically.
How do I convert kilohms to ohms?
Multiply kilohms by 1,000. For example, 10 kΩ = 10,000 Ω.
What is the power triangle?
The power triangle shows the relationship between real power (P), apparent power (S), and reactive power (Q) in AC circuits. It is related to Ohm's Law through the power factor.
Can I use this calculator for 3-phase circuits?
This calculator is designed for DC and single-phase AC circuits. For 3-phase calculations, additional factors like power factor and line-to-line voltage are needed. Use our 3-phase power calculator for those calculations.
What is the difference between a series and parallel circuit?
In a series circuit, components are connected end-to-end, and the same current flows through all components. In a parallel circuit, components are connected across the same voltage source, and the voltage is the same across all components. Ohm's Law applies to both types of circuits.
How does temperature affect resistance?
For most conductors, resistance increases with temperature. For semiconductors, resistance decreases with temperature. This calculator assumes constant temperature conditions.
What is the maximum current a wire can carry?
The maximum current depends on the wire gauge, material, insulation type, and ambient temperature. Use our Wire Size Calculator to determine the appropriate wire size for your application.
How do I calculate the voltage drop in a circuit?
Voltage drop = Current × Resistance of the conductor. Our Voltage Drop Calculator can help you determine the voltage drop in a circuit.
Is Ohm's Law always accurate?
Ohm's Law is accurate for linear conductors where resistance remains constant regardless of voltage and current. For non-linear devices like diodes and transistors, Ohm's Law is not directly applicable.