Electrical reference chart
HP to Amps Chart
Use this motor-current screen when horsepower is known but the project still needs nameplate FLA, starting current, protection, or conductor review.
Quick reference table
HP-to-amps is a motor load estimate, not a substitute for motor nameplate FLA or NEC motor full-load current workflows. A 10 HP at 480 V 3-phase motor estimates about 11.2 A with the chart assumptions. Use it early when reviewing a pump, fan, compressor, conveyor, or shop motor schedule, then move to the motor calculator with voltage, phase, efficiency, power factor, nameplate current, and starting-current context.
Formula-based motor running-current screen
| Motor size | 240 V 1-phase | 208 V 3-phase | 480 V 3-phase | Assumption |
|---|---|---|---|---|
| 1 HP | 4.3 A | 3.0 A | 1.3 A | 90% eff, 0.80 PF |
| 3 HP | 13.0 A | 9.0 A | 3.9 A | 90% eff, 0.80 PF |
| 5 HP | 21.6 A | 15.0 A | 5.6 A | 90% eff, 0.80 PF |
| 10 HP | 43.2 A | 29.9 A | 11.2 A | 90% eff, 0.80 PF |
| 25 HP | 107.9 A | 74.8 A | 28.1 A | 90% eff, 0.80 PF |
Which motor current value belongs in which decision
| Decision | Current basis to verify | Why the chart is not enough |
|---|---|---|
| Load estimate | Formula current or nameplate input current | Good for early panel or generator screening |
| Conductor and branch circuit | Adopted motor sizing path and table/nameplate basis | Motor rules can differ from formula current |
| Overload protection | Motor nameplate current and overload instructions | Nameplate FLA is usually central |
| Starting review | Locked-rotor, inrush, or starter method | Running current does not show voltage dip |
How to use this chart
Use it before the nameplate is complete
Use the chart for early pump, fan, compressor, conveyor, or shop-equipment screening when horsepower is known but full motor data is not ready.
Record motor phase and voltage
Write the actual motor connection voltage and whether the motor is single-phase or three-phase before comparing rows.
Separate running and starting current
Use this page for running-current estimates only, then use the starting-current workflow for inrush, voltage dip, or generator sizing concerns.
Move code work to the motor calculator
Before conductors or protection are selected, use the motor calculator and verify nameplate, adopted NEC, manufacturer, and AHJ requirements.
Formula basis
Single phase estimate: A = HP x 746 / (V x efficiency x PF). Three phase estimate: A = HP x 746 / (1.732 x VLL x efficiency x PF).
- HP is mechanical horsepower.
- Efficiency is motor efficiency entered as a decimal.
- PF is motor power factor entered as a decimal.
- V or VLL is the voltage used by the motor connection.
Worked examples
5 HP fan motor at 480 V three-phase
5 x 746 / (1.732 x 480 x 0.90 x 0.80) = about 6.2 A as a running-current screen before nameplate and protection review.
3 HP single-phase shop motor at 240 V
3 x 746 / (240 x 0.88 x 0.78) = about 13.6 A using the documented efficiency and PF assumptions.
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Frequently asked questions
These answers explain how to use the chart without turning a quick reference into a final design decision.