3 Phase Motor Amperage Calculator
Estimate three-phase motor line current from shaft horsepower or kilowatts, line voltage, efficiency and power factor. Enter your own values and review every assumption shown with the result.
Use this calculator on your website
Add this free 3 Phase Motor Amperage Calculator to your blog, article, or business website. Copy the embed code and publish it in minutes.
Perfect for blogs, WordPress, Webflow, and business websites.
The primary result is displayed first, followed by supporting values that make the estimate easier to verify.
Need a calculator like this?
Calciro can build a custom calculator around your formulas, pricing rules, or lead-generation process.
How to Use This Calculator
Enter each requested value using the displayed unit. Replace the example defaults with source-specific values and review all assumptions.
Formula & Methodology
The calculator applies the displayed formulas directly to the entered values. Supporting outputs expose important intermediate calculations.
Worked example
A 15 kW motor at 480 V, 90% efficiency and 0.85 power factor draws an estimated 23.6 A under the simplified balanced three-phase formula.
Nameplate current and code table full-load current may differ. Starting current, load variation, voltage imbalance, harmonics, motor design, duty and drive efficiency are not modeled.
Use the motor nameplate, manufacturer data and applicable electrical code for conductor, overload and short-circuit protection sizing. Qualified electrical design is required.
Related Calculators
- 3 Phase Power CalculatorCalculate three-phase real power, apparent power and reactive power from line voltage, current and power factor.
- Amps to kW CalculatorConvert amps to kilowatts for single-phase and three-phase electrical loads.
- Electrical Load CalculatorEstimate total electrical demand, apparent power and current from connected load, demand factor, voltage, phase factor and power factor.
- Watts to Amps CalculatorConvert watts to amps for DC, single-phase AC or three-phase AC circuits using voltage, power factor and efficiency.
Related Guides
- How Three-Phase Motor Amperage Is Calculated from HP and VoltageLearn the three-phase motor current formula — how to calculate full-load amps from horsepower, voltage, motor efficiency, and power factor, with NEC table values for quick reference.
- How to Convert Amps to Kilowatts: Single-Phase and Three-Phase FormulasConvert amps to kilowatts using the correct formula for single-phase or three-phase circuits. Covers power factor, worked examples, and a quick reference table.
- How to Calculate the Right Fuse Size for Electrical CircuitsLearn how to determine the correct fuse or circuit breaker size for any electrical circuit — based on load current, conductor size, NEC overcurrent protection rules, and motor starting current.
- How to Convert Amp Hours to Watt HoursLearn how to use the Amp Hour to Watt Hour Calculator, understand its formula and interpret the result.
- How Manual D Friction Rate and Duct Sizing WorksUnderstand how ACCA Manual D duct design works — how available static pressure and friction rate determine duct sizes, and how to calculate CFM requirements for each room.
Frequently Asked Questions
- What does the 3 Phase Motor Amperage Calculator calculate?
- Estimate three-phase motor line current from shaft horsepower or kilowatts, line voltage, efficiency and power factor.
- Can I change the assumptions?
- Yes. Replace the example defaults with values from the current game, project, product, drawing, data sheet or market source.
- Is the result exact?
- No. It is an estimate produced by the displayed formulas and entered assumptions. Real results may differ because of factors described in the limitations section.
- Should an important result be verified?
- Yes. Verify important decisions with current source data, official documentation, manufacturer information or a qualified professional.
Last updated 7/22/2026