Online Ohm's Law Calculator
Calculate Voltage (V), Current (I), Resistance (R), and Power (P). Simply enter two known values to solve for the rest.
Awaiting Input...
Fill in any 2 boxes on the left to solve.
The Four Pillars of Electricity
Understanding the relationship between V, I, R, and P is fundamental to all electronics.
Voltage (Volts)
The "pressure" that pushes electricity. Like water pressure in a hose.
V = P / I
Current (Amps)
The "flow rate" of electricity. Like the amount of water flowing through the hose.
I = P / V
Resistance (Ohms)
The "friction" opposing flow. Like narrowing the hose, restricting the water.
R = V² / P
Power (Watts)
The "work done" by electricity. The total force and flow combining to perform a task.
P = I² × R
Frequently Asked Questions
What is Ohm's Law?
Ohm's Law states that the current flowing through a conductor between two points is directly proportional to the voltage across the two points. The standard formula is V = I × R, where V is voltage, I is current, and R is resistance.
What are the basic units used?
Voltage (V) is measured in Volts (V). Current (I) is measured in Amperes or Amps (A). Resistance (R) is measured in Ohms (Ω). Power (P) is measured in Watts (W).
How is Power related to Ohm's Law?
While Ohm's Law strictly deals with V, I, and R, Joule's law helps us find Power (P). Power is the rate at which electrical energy is transferred by an electric circuit. The fundamental formula for power is P = V × I. By substituting Ohm's Law into this equation, you can also get P = I²R or P = V² / R.
Why do I need to enter exactly 2 values?
The relationships between Voltage, Current, Resistance, and Power form a complete mathematical system. If you know any two of these values, the formulas allow you to perfectly calculate the other two. Entering only one value doesn't provide enough information, and entering three might create contradictions if they don't align mathematically.
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