Volts to Amps Calculator
Understand the relationship between voltage and current. Calculate precisely how many amperes will result from a given voltage and power load.
Current Analysis
Voltage + Power → Amps
The resulting current flow that will occur on the circuit.
The Conversion Formula
Current calculation changes depending on whether your circuit is DC or AC — and on the power factor for AC systems.
DC Systems
I = (kW × 1000) ÷ V Direct current has no phase angle — current is simply power divided by voltage.
1-Phase AC
I = (kW × 1000) ÷ (V × PF) Power factor reduces effective power in AC circuits. A PF of 0.9 means 10% more current is drawn than the real power suggests.
3-Phase AC
I = (kW × 1000) ÷ (√3 × V × PF) Three-phase power is distributed across three conductors — the √3 (1.732) factor accounts for the phase relationship between them.
How to Convert Volts to Amps
Converting voltage to current requires knowing the power being consumed or the resistance in the circuit. When you know power (in kW or W), Ohm's Law and the power formula give you current directly. This calculation is essential for sizing circuit breakers, fuses, wire gauges, and selecting protective equipment.
Why Voltage and Current Move in Opposite Directions
For a fixed load, doubling the voltage halves the current. This inverse relationship is why high-voltage transmission lines carry massive power across long distances using thin cables — lower current means less resistive heating and power loss in the wire.
Practical Applications
- Circuit Breaker Sizing: A 2kW heater on 240V single-phase draws about 8.7A at unity PF — you'd protect it with a 10A or 15A breaker.
- Wire Gauge Selection: Higher current requires thicker wire to stay within safe temperature limits. Use the NEC or IEC ampacity tables after calculating current.
- Fuse Selection: Fuses must be rated at 125% of continuous load current. Calculate first, then select the fuse size.
- Motor Nameplate Verification: Cross-check the listed FLA (Full Load Amps) against the calculated current from rated HP and voltage.
Step-by-Step Conversion
- Note the Power: Find the kW or watt rating on the equipment label.
- Read the Voltage: Confirm the system voltage — check the supply panel or equipment nameplate.
- Identify AC or DC: DC circuits use the simple formula; AC circuits need the power factor applied.
- Calculate and Size Up: Always round up to the next standard breaker or fuse size after calculating.