Basic Electrical Laws calculator
Current Calculator
This professional current calculator implements Ohm's Law (I = V/R) and power relationships (P = V×I, P = I²R) for DC and single-phase AC resistive circuits. Enter voltage and resistance to find current flow in amperes, or use power and voltage to calculate current draw for load analysis. Results help electricians verify branch circuit loading, check conductor ampacity requirements, and validate breaker sizing against NEC guidelines. The calculator displays both the calculated current and equivalent power consumption, providing essential data for circuit design and troubleshooting.
Updated July 16, 2026
Example Calculations
How to Use
How to Use the Current Calculator
1. Choose which values you know: voltage and resistance, voltage and power, or current and resistance.
2. Enter the known values with the correct units (volts, ohms, watts).
3. Click Calculate to compute current and the remaining electrical quantities.
4. Use the results to check circuit loading, breaker sizing and basic design assumptions.
Current calculations stem from Ohm's Law I = V/R—for the full derivation and variant formulas, see our Ohm's Law Formulas Guide. For wire sizing based on current capacity, use the Ampacity Calculator.
Common Applications
Frequently Asked Questions
What formula does this current calculator use?
For DC and resistive AC circuits, the calculator uses Ohm's Law: I = V/R and power relationships P = V×I and P = I²R. From any two known values it solves for the others.
Can I use this for three-phase motors?
This calculator is intended for simple DC and single-phase AC circuits. For three-phase motors and NEC-oriented sizing, use the dedicated motor current and load calculators on EleCalculator.
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