Electronics Calculator
Ohm's Law Calculator
Enter any two values — voltage, current, resistance, or power — and all four are solved instantly using Ohm's Law and the power formula.
Solve V · I · R · P
Fill in any two fields. The remaining values are calculated automatically.
Volts
Amps
Ohms (Ω)
Watts
Enter any two values above…
All four values will appear here
Ohm's Law Triangle
Core Formulas:
V = I × R (Voltage = Current × Resistance)
I = V / R (Current = Voltage / Resistance)
R = V / I (Resistance = Voltage / Current)
Power Formulas:
P = V × I (Power = Voltage × Current)
P = I² × R (Power = Current² × Resistance)
P = V² / R (Power = Voltage² / Resistance)
V = I × R (Voltage = Current × Resistance)
I = V / R (Current = Voltage / Resistance)
R = V / I (Resistance = Voltage / Current)
Power Formulas:
P = V × I (Power = Voltage × Current)
P = I² × R (Power = Current² × Resistance)
P = V² / R (Power = Voltage² / Resistance)
Quick Reference
Units:
V = Volts (V) · I = Amps (A) or milliamps (mA)
R = Ohms (Ω), kΩ, MΩ · P = Watts (W)
Common conversions:
1 mA = 0.001 A · 1 kΩ = 1000 Ω · 1 mW = 0.001 W
Example — LED circuit:
Supply = 5V, LED Vf = 2V, so V across resistor = 3V
Desired I = 20mA = 0.02A → R = 3 / 0.02 = 150 Ω
V = Volts (V) · I = Amps (A) or milliamps (mA)
R = Ohms (Ω), kΩ, MΩ · P = Watts (W)
Common conversions:
1 mA = 0.001 A · 1 kΩ = 1000 Ω · 1 mW = 0.001 W
Example — LED circuit:
Supply = 5V, LED Vf = 2V, so V across resistor = 3V
Desired I = 20mA = 0.02A → R = 3 / 0.02 = 150 Ω