Volts to Amps Calculator
Calculate electrical current (amperage) from voltage and power for AC circuits.
Power Formula
P = V × I conversions
Volts to Amps Calculator
Convert voltage and power to current for electrical circuits
Input Parameters
Line voltage (120 V, 240 V, 480 V, etc.)
Real power consumption in watts
Enter the power factor from the equipment nameplate. Resistive loads such as heaters have a power factor of 1.
Calculation Results
| Voltage | Current |
|---|---|
| 120 V | 8.3 A |
| 240 V | 4.2 A |
| 480 V | 2.1 A |
Understanding Ohm's Law & Power Formulas
Fundamental Formulas
Ohm's Law
V = I × R
- • V = Voltage (volts)
- • I = Current (amps)
- • R = Resistance (ohms)
Power Law
P = V × I
- • P = Power (watts)
- • V = Voltage (volts)
- • I = Current (amps)
Combined Formula
P = I² × R = V² ÷ R
- • Use when missing voltage or current
- • Critical for power loss calculations
Formula Wheel
To find Voltage:
V = I × R
V = P ÷ I
V = √(P × R)
To find Current:
I = V ÷ R
I = P ÷ V
I = √(P ÷ R)
To find Resistance:
R = V ÷ I
R = V² ÷ P
R = P ÷ I²
To find Power:
P = V × I
P = I² × R
P = V² ÷ R
AC vs DC Current Calculations
DC Circuit Calculations
Simple Formula:
I = P ÷ V
No power factor consideration needed
Common DC Applications:
- ▶12 V Systems: Automotive, RV, Marine
- ▶24 V Systems: Trucks, Industrial controls
- ▶48 V Systems: Telecom, Data centers
- ▶High Voltage DC: Solar strings, EV charging
AC Circuit Calculations
Single-Phase Formula:
I = P ÷ (V × PF)
Three-Phase Formula:
I = P ÷ (V × √3 × PF)
Impact of Voltage on Current Draw
Understanding how voltage variations affect current is critical for proper circuit design:
Low Voltage Effects
- • Motors draw MORE current
- • Increased heat generation
- • Reduced equipment life
- • Potential motor stalling
- • Dimming lights
Example: 10 % voltage drop
= 11 % current increase
Nominal Voltage
- • Equipment runs as designed
- • Optimal efficiency
- • Expected lifespan
- • Proper power output
- • Normal operating temp
High Voltage Effects
- • Motors draw LESS current
- • Increased insulation stress
- • Shortened bulb life
- • Electronic damage risk
- • Overvoltage trips
Example: 10 % overvoltage
= Reduced equipment life
Related Electrical Calculators
Important Safety Information
Electrical calculations must be verified by qualified professionals before implementation. Current calculations determine wire size, breaker ratings, and equipment specifications. Undersized conductors can cause fires, while oversized protection may not trip during faults. Always follow NEC requirements, consider all derating factors, and have work inspected by local authorities. Never work on live circuits.