Ohm's Law & Power Calculator (Enhanced)
Solve Ohm's Law for current, voltage, resistance, and power. Enter any two known values to calculate the rest � ideal for quick circuit analysis and component selection.
Results
What is it?
Ohm's Law defines the relationship between voltage (V), current (I), and resistance (R): V = IR. Power P = V � I = I�R = V�/R. This enhanced calculator solves for current given voltage and resistance, or uses a manually entered current for power calculations. Energy per hour = P � 1 hour (in Wh).
How to use
Enter the voltage and resistance. Leave current as 0 to auto-calculate I = V/R. Or enter a known current to override (e.g., when resistance is non-linear or when analyzing a constant-current circuit). All power relationships are derived from the resulting V and I.
Example scenario
12V supply across a 100O resistor: I = 12/100 = 0.12 A = 120 mA. Power = 12 � 0.12 = 1.44 W. Energy per hour = 1.44 Wh. A 1/4W resistor would be inadequate here � use at least a 2W resistor with margin.
Pro tip
Always choose resistors with a power rating at least 2� the calculated dissipation for reliability and temperature derating. In real circuits, Ohm's Law applies to linear resistors � semiconductors (diodes, transistors, LEDs) and reactive components (capacitors, inductors) behave differently. Use a SPICE simulator (LTspice is free) for complex circuit analysis.