Ohm's Law Calculator

Solve for voltage, current, or resistance from any two values. Also shows power (watts).
A
Ω

Voltage

12.000 V

Current

2.000 A

Resistance

6.000 Ω

All Values

Voltage (V)12.000 V
Current (I)2.000 A
Resistance (R)6.000 Ω
Power (P)24.000 W
FormulaV = I × R

Use the Ohm's Law Calculator above to calculate your results. Enter your values and see instant results — all calculations run in your browser.

Disclaimer: This calculator is for informational purposes only and does not constitute tax, financial, or legal advice. Results are estimates based on the information you provide and current rates. Always consult a qualified tax professional or financial advisor for advice specific to your situation.

How It Works

Our Ohm's Law Calculator is an essential tool for engineers, technicians, and hobbyists working with electrical circuits. This calculator allows you to quickly solve for voltage, current, or resistance when any two values are known, and it simultaneously calculates the power (watts) dissipated in the circuit. In 2026, with the increasing prevalence of IoT devices and smart home technology, understanding these fundamental electrical relationships is more crucial than ever for efficient design and troubleshooting.

This calculator utilizes Ohm's Law, which states the relationship between voltage (V), current (I), and resistance (R) as V = I * R. It also incorporates the power formula, P = V * I, to calculate the power dissipated in the circuit. By inputting any two of the primary values (V, I, or R), the calculator rearranges these formulas to solve for the missing primary value and then subsequently calculates the power.

When using the calculator, ensure your units are consistent (volts, amperes, ohms). A common mistake is confusing resistance (ohms) with conductance (siemens), or misinterpreting the difference between DC and AC circuits, though Ohm's Law primarily applies to DC or instantaneous AC values. Always double-check your input values to avoid calculation errors.

Example: Powering a Smart LED Strip in 2026

  1. 1 Imagine you're designing a smart home lighting system in 2026, and you have an LED strip that requires 12V and has a total resistance of 24 Ohms. You want to know the current it draws and the power it consumes.
  2. 2 Input Voltage (V) = 12V, Resistance (R) = 24 Ohms. The calculator will use I = V / R and P = V * I.
  3. 3 Calculated Current (I) = 0.5 Amperes, Calculated Power (P) = 6 Watts.
  4. 4 This means your 12V LED strip will draw 0.5 Amperes of current and consume 6 Watts of power. This information is vital for selecting the correct power supply unit (PSU) and ensuring your circuit design can safely handle the load, preventing overheating or component failure, which is especially important for the longevity of smart home devices.

Source: Khan Academy · Last updated: April 2026

Frequently Asked Questions

What is Ohm's Law?
Ohm's Law states that voltage (V) equals current (I) times resistance (R): V = IR. You can rearrange to find any value: I = V/R or R = V/I. It is the foundational equation for electrical circuits.
How do you calculate watts from volts and amps?
Power (watts) = voltage x current. For a 120V outlet drawing 10 amps: 120 x 10 = 1,200 watts. You can also calculate: P = I²R or P = V²/R.
What is the resistance of a 60-watt light bulb?
At 120V: R = V²/P = 120²/60 = 240 ohms. The current draw is I = P/V = 60/120 = 0.5 amps. Note that actual resistance varies with filament temperature.

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