Calculate Voltage, Current, Resistance, and Power
Enter any two values to calculate the others
Voltage
V = I × R
Current
I = V ÷ R
Resistance
R = V ÷ I
Power
P = V × I
Ohm's Law states that the current through a conductor between two points is directly proportional to the voltage across the two points.
Our comprehensive Ohm's Law Calculator helps students, engineers, and electronics enthusiasts calculate voltage, current, resistance, and power with precision. Solve complex electrical circuits, verify calculations, and understand fundamental electrical principles with ease.
Calculate voltage, current, resistance, and power simultaneously using all Ohm's Law formulas and power equations.
Learn electrical principles with detailed formula explanations, unit conversions, and practical examples.
Get wire gauge recommendations, fuse ratings, and safety warnings based on calculated current and power values.
Design and analyze series, parallel, and combination circuits with component selection guidance.
Build a solid foundation in electrical theory with precise calculations that help you understand, design, and troubleshoot electronic circuits with confidence and accuracy.
V = I × R
Voltage = Current × Resistance
I = V ÷ R
Current = Voltage ÷ Resistance
R = V ÷ I
Resistance = Voltage ÷ Current
P = V × I
Power = Voltage × Current
P = I² × R
Power = Current² × Resistance
P = V² ÷ R
Power = Voltage² ÷ Resistance
Calculate circuit loads, wire sizing, and breaker requirements
Design and analyze electronic circuits and components
Calculate automotive electrical system requirements
Ohm's Law is the fundamental principle in electrical engineering that defines the relationship between voltage, current, and resistance. It states that V = I × R, where V is voltage in volts, I is current in amperes, and R is resistance in ohms. This law is essential for designing, analyzing, and troubleshooting electrical circuits.
Electrical power can be calculated using three different formulas derived from Ohm's Law: P = V × I, P = I² × R, or P = V² ÷ R. Use the formula that matches your known values. For example, if you know current and resistance, use P = I² × R.
Standard units are: Voltage (V) in volts, Current (I) in amperes, Resistance (R) in ohms, and Power (P) in watts. Common prefixes include milli- (m), kilo- (k), and mega- (M) for dealing with very small or very large values.
Residential circuits typically handle 15-20A; never exceed rated capacities
Use correct wire gauge based on calculated current requirements
Always use appropriately rated fuses or circuit breakers
Household voltage can be dangerous; always work with power off