The number on the motor plate is not the number that sizes the feeder. NEC Tables 430.248 (single-phase) and 430.250 (three-phase) publish a planning full-load current by horsepower and voltage. Conductors and branch-circuit short-circuit / ground-fault protection use that table FLC. Overload heaters use the nameplate FLA. This is a lookup, not a substitute for the NEC or a licensed electrician.
The number on the motor plate is not the number that sizes the feeder.
Use it when wiring a shop motor — a table saw, a dust collector, a compressor — and you need the full-load current from the standard table, which is what conductor and short-circuit protection sizing normally start from under the NEC. Pick the horsepower, voltage and phase. The nameplate current is still the figure for overload settings.
This page does not compute current from horsepower, efficiency, or power factor. It reads a stored planning value that matches the commonly published entries in NEC Table 430.248 (single-phase AC motors) or NEC Table 430.250 (three-phase AC induction motors). Those tables exist so a 10 HP, 460 V motor gets the same feeder current whether the plate says 12.7 A or 14.2 A.
Lookup: FLC = Table(HP, V, phase)
Table 430.248 columns: 115, 200, 208, 230 V. Table 430.250 columns: 115, 200, 208, 230, 460, 575, 2300 V.
Listed motor volts also cover the usual system ranges: 110–120, 220–240, 440–480, 550–600 V. Pick 460 V for a 480 V bus.
430.6(A)(1) — table FLC sizes conductors, switches, and branch-circuit short-circuit / ground-fault protection.
430.6(A)(2) — nameplate FLA sizes separate overload devices.
Continuous-duty single-motor conductor planning check: Icond = 1.25 × table FLC (430.22). This page does not pick a wire or a breaker.
Low-speed motors (under 1,200 rpm), high-torque machines, canned pumps, and multispeed motors are outside these usual-speed rows — the adopted code sends you to the nameplate for those. Synchronous-motor columns in 430.250 are not on this calculator. Confirm every number against the edition and amendments your jurisdiction adopted. NFPA 70 / NEC is the NFPA’s document; this worksheet is not it.
| Case | Table | FLC |
|---|---|---|
| 10 HP, 460 V, 3φ | 430.250 | 14 A |
| 5 HP, 230 V, 1φ | 430.248 | 28 A |
| 1 HP, 230 V, 3φ | 430.250 | 4.2 A |
| 25 HP, 460 V, 3φ | 430.250 | 34 A |
| 10 HP, 230 V, 1φ | 430.248 | 50 A |
| 5 HP, 460 V, 3φ | 430.250 | 7.6 A |
Those six rows come from the same table the calculator uses. The first row is the default example: a typical 10 HP, 460 V three-phase motor is 14 A table FLC. A 5 HP, 230 V single-phase motor is 28 A — nearly double the 15.2 A three-phase figure at the same horsepower and voltage. That is why the phase field is not optional.
Nameplate FLA is the current that motor actually draws at rated load. Table FLC is a standardized planning current for that horsepower and voltage. 430.6 splits them on purpose: the feeder and the short-circuit device have to survive a replacement motor from a different maker, so they follow the table. The overload is protecting this winding, so it follows the plate. Putting the plate current on the breaker is the usual exam trap and a common field error.
The 460 V column. The tables list rated motor voltages and permit those currents on the matching system ranges — 440 to 480 V uses the 460 V row, 220 to 240 V uses 230 V, 110 to 120 V uses 115 V, 550 to 600 V uses 575 V. A 208 V motor is its own column, not 230 V rounded down.
No. You get table FLC, an optional nameplate field, and a 125% conductor-ampacity check for a single continuous-duty motor. Inverse-time breaker percentages, dual-element fuses, instantaneous trip, Design B vs wound-rotor, ambient, grouping, termination temperature, and 430.52 “next standard size” are not on this calculator. That is licensed work against the book in force, not a webpage.
Different tables, different current. 5 HP at 230 V is 28 A single-phase (430.248) and 15.2 A three-phase (430.250). Using the three-phase row on a well pump or a shop compressor that is actually single-phase undersizes the circuit. Read the plate for phase before you pick the dropdown.
Some combinations are blank in the table. Three-phase 115 V stops at 2 HP. 200 V and 208 V three-phase stop before the largest machines. 2300 V starts at 60 HP. Single-phase stops at 10 HP. This page will not invent a current for a blank cell. Use another listed voltage, or take the nameplate and the adopted code — including the 430.6 exceptions for odd-speed and high-torque motors.
No. It is a planning lookup of stored table values plus an optional nameplate box. It is not a code opinion, not an inspection, not a design, and not permission to land a feeder. Confirm the horsepower, the voltage column, and the edition in force with a licensed electrician before you pull wire.