How do I calculate Voltage, Current, or Resistance?

To find Voltage (V), multiply Current by Resistance (V = I × R). To find Current (I), divide Voltage by Resistance (I = V / R). To find Resistance (R), divide Voltage by Current (R = V / I).

How does the calculator handle division by zero?

When calculating Current with a resistance of 0 Ω, the calculator alerts you that resistance cannot be zero, as an ideal 0 Ω path represents a theoretical short circuit resulting in infinite current. Similarly, when calculating Resistance with 0 A current, it indicates an open circuit where resistance is infinitely large.

Can I use smaller or larger units like mA or kΩ?

Yes! The calculator features built-in unit pickers for Voltage (µV, mV, V, kV), Current (µA, mA, A, kA), and Resistance (mΩ, Ω, kΩ, MΩ). Values are automatically normalized to base SI units for calculation and displayed with human-friendly engineering notation.

How is electrical power (Watts) calculated?

Electrical power (P) is the rate at which electrical energy is transferred or dissipated as heat. It is calculated alongside Ohm's Law using P = V × I. By substitution, power can also be calculated using P = I² × R or P = V² / R.

Does this tool transmit circuit data to a server?

No. All physics computations, unit conversions, and formula evaluations execute 100% locally in your browser sandbox with zero network transmission, ensuring total privacy and instant real-time response.

Ohm's Law Calculator

Q: What is Ohm's Law?

Ohm's Law is a fundamental principle of electrical physics stating that the electric current (I) flowing through a conductor between two points is directly proportional to the voltage (V) across the two points and inversely proportional to the resistance (R) of the conductor. It is expressed by the formula V = I × R.

Calculate Voltage (V), Current (I), Resistance (R), and Power (P) in real-time. Features multi-unit conversion, division-by-zero protection, and step-by-step circuit formulas.

Live

Volts
Amps
Ohms
Watts

Ohm's Law Calculator

Calculate Voltage, Current, Resistance, and Power in real time with multi-unit conversion and instant error handling.

100% Client-Side

What do you want to calculate?Ohm's Law: V = I × R

Quick circuit presets:

Current (I)

Rate of electrical charge flow per second.

Resistance (R)

Opposition to electrical current flow in the circuit.

Calculated VoltageV = I × R

12 V

V = I × R = 2 A × 6 Ω

Includes power & formula step

Electric Power (P)24 WP = V × I

Total Voltage (V)12 VPotential

Total Current (I)2 ACharge flow

Resistance (R)6 ΩOpposition

What is Ohm's Law?

Ohm's Law is a fundamental formula in electrical physics describing the linear relationship between voltage, current, and resistance in an electrical circuit: V = I × R. It states that the electric current passing through a conductor between two points is directly proportional to the voltage applied across those points, provided the temperature remains constant.

Voltage (V)

Measured in Volts (V)

The electrical pressure or potential difference that pushes charges through the circuit.

Current (I)

Measured in Amperes (A)

The volume and rate at which electrons and electric charge flow past a given point per second.

Resistance (R)

Measured in Ohms (Ω)

The physical opposition material offers to the flow of electric current, converting energy into heat.

How to use the Ohm's Law Calculator?

Follow these step-by-step instructions to solve any DC or single-phase resistive AC circuit variable in seconds:

1
Choose what you want to calculate:
Select between Find Voltage (V), Find Current (I), or Find Resistance (R) from the selector tabs above.
2
Enter the two known circuit values:
Type your values into the corresponding input fields. You can also pick popular pre-configured benchmarks like LED current or USB power.
3
Select appropriate engineering units:
Choose units from the dropdown menus (e.g. mA for low currents, kV for power lines, kΩ or MΩ for resistors).
4
View instant real-time results and power:
The missing parameter, applied formula, mathematical substitution, and total electrical power dissipation (Watts) update live as you type.
5
Copy or Reset:
Click "Copy Result" to copy the answer with circuit breakdown to your clipboard, or click "Reset" to start a fresh calculation.

Formula Reference Table

Quick-reference matrix of Ohm's Law and Joule's Law equations for calculating Voltage, Current, Resistance, and Power:

To Find	Primary Formula	Alternative (with Power P)	SI Unit & Symbol
Voltage (V)	V = I × R	V = P / I = √(P × R)	Volts (V)
Current (I)	I = V / R	I = P / V = √(P / R)	Amperes (A)
Resistance (R)	R = V / I	R = V² / P = P / I²	Ohms (Ω)
Power (P)	P = V × I	P = I² × R = V² / R	Watts (W)

Frequently Asked Questions

Everything you need to know about Ohm's Law, practical circuit design, and error handling.

In Ohm's Law (I = V / R), dividing any non-zero voltage by zero resistance mathematically yields infinity. In physical circuits, this is called a dead short circuit: current spikes extremely rapidly until wires melt, traces burn, or a circuit breaker trips. The calculator prevents division by zero to reflect this physical boundary.

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To Find

Primary Formula

Alternative (with Power P)

SI Unit & Symbol

Voltage (V)

V = I × R

V = P / I = √(P × R)

Volts (V)

Current (I)

I = V / R

I = P / V = √(P / R)

Amperes (A)

Resistance (R)

R = V / I

R = V² / P = P / I²

Ohms (Ω)

Power (P)

P = V × I

P = I² × R = V² / R

Watts (W)

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Ohm's Law Calculator

Ohm's Law Calculator

What is Ohm's Law?

How to use the Ohm's Law Calculator?

Formula Reference Table

Frequently Asked Questions

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Frequently Asked Questions