What is Full-Load Amps (FLA)?

FLA is the current a motor draws at its rated horsepower, voltage, and frequency under full mechanical load. NEC Tables 430.248 (single-phase) and 430.250 (three-phase) list standard full-load currents (FLC) used for circuit sizing; the nameplate FLA is used for overload protection.

Why does NEC use table values instead of nameplate FLA?

NEC 430.6(A)(1) requires the table values for ampacity of conductors, switches, and branch-circuit short-circuit and ground-fault protection, so a replacement motor with a higher nameplate current does not leave the circuit undersized. Exceptions include low-speed (under 1200 RPM), high-torque, and multispeed motors, which use nameplate current.

How do I size a breaker from the FLA result?

Per NEC 430.52 and Table 430.52(C)(1), an inverse-time breaker may be up to 250% of the table full-load current, and the next standard size is allowed when that is not a standard rating. Example: 28 A × 2.5 = 70 A breaker. If the motor will not start, 430.52(C)(1) Exception 2 allows an inverse-time breaker up to 400% for full-load currents of 100 A or less (300% above 100 A).

What size wire do I need for a motor?

Multiply the table full-load current by 1.25 (NEC 430.22) and choose a conductor whose ampacity meets it. A 10 HP, 230 V three-phase motor is 28 A × 1.25 = 35 A, which is 10 AWG copper at 75 °C or 8 AWG at 60 °C. Correct for ambient temperature, more than three current-carrying conductors, and voltage drop on long runs.

How do I set the overload relay?

Use the motor nameplate current, not the table. NEC 430.32(A)(1) allows 125% for motors marked with a service factor of 1.15 or more or a temperature rise of 40 °C or less, and 115% for all others. Example: 26 A nameplate, SF 1.15 → 32.5 A.

What if my horsepower is not in the NEC table?

This calculator uses the next larger listed horsepower for that voltage, which never under-sizes the circuit, and shows the straight-line interpolated value for reference. For kW-rated motors it converts at 746 W per HP first.

Can I calculate motor amps from horsepower with a formula?

Yes, as an estimate: single-phase I = HP × 746 ÷ (V × efficiency × PF); three-phase I = HP × 746 ÷ (1.732 × V × efficiency × PF). Real efficiency and power factor vary with size and load, which is why the NEC tables are used for circuit design.

Does this cover every motor type?

No. The tables cover single-phase and three-phase induction motors. DC motors (Table 430.247), synchronous motors, wound-rotor, torque, multispeed and other special motors require their applicable NEC rules and nameplate data.

Motor Full-Load Amps Calculator

Enter motor horsepower (or kW), voltage and phase to get the NEC table full-load current, then the 250% breaker, 175% fuse, 125% conductor size in AWG and the nameplate-based overload setting.

Motor Parameters

Motor Phase

Single-Phase Three-Phase

Voltage (V)

Motor rating

Overload sizing (optional, NEC 430.32)

Nameplate FLA (A)

Nameplate marking

Formula estimate (comparison only)

Efficiency (%)

Power factor

Results

Enter motor parameters and click Calculate.

NEC Motor Full-Load Current Tables

Full-load current in amperes. The calculator highlights the row it used.

Table 430.248 — Single-Phase AC Motors

HP	115 V	200 V	208 V	230 V
1/6	4.4	2.5	2.4	2.2
1/4	5.8	3.3	3.2	2.9
1/3	7.2	4.1	4	3.6
1/2	9.8	5.6	5.4	4.9
3/4	13.8	7.9	7.6	6.9
1	16	9.2	8.8	8
1-1/2	20	11.5	11	10
2	24	13.8	13.2	12
3	34	19.6	18.7	17
5	56	32.2	30.8	28
7-1/2	80	46	44	40
10	100	57.5	55	50

Table 430.250 — Three-Phase AC Induction Motors

HP	115 V	200 V	208 V	230 V	460 V	575 V	2300 V
1/2	4.4	2.5	2.4	2.2	1.1	0.9	—
3/4	6.4	3.7	3.5	3.2	1.6	1.3	—
1	8.4	4.8	4.6	4.2	2.1	1.7	—
1-1/2	12	6.9	6.6	6	3	2.4	—
2	13.6	7.8	7.5	6.8	3.4	2.7	—
3	—	11	10.6	9.6	4.8	3.9	—
5	—	17.5	16.7	15.2	7.6	6.1	—
7-1/2	—	25.3	24.2	22	11	9	—
10	—	32.2	30.8	28	14	11	—
15	—	48.3	46.2	42	21	17	—
20	—	62.1	59.4	54	27	22	—
25	—	78.2	74.8	68	34	27	—
30	—	92	88	80	40	32	—
40	—	120	114	104	52	41	—
50	—	150	143	130	65	52	—
60	—	177	169	154	77	62	16
75	—	221	211	192	96	77	20
100	—	285	273	248	124	99	26
125	—	359	343	312	156	125	31
150	—	414	396	360	180	144	37
200	—	552	528	480	240	192	49
250	—	—	—	—	302	242	60
300	—	—	—	—	361	289	72
350	—	—	—	—	414	336	83
400	—	—	—	—	477	382	95
450	—	—	—	—	515	412	103
500	—	—	—	—	590	472	118

Use the 110–120, 220–240 and 440–480 V system voltages with the 115, 230 and 460 V columns (Table 430.248/430.250 notes). Synchronous motors, DC motors (Table 430.247) and low-speed, high-torque or multispeed motors are not covered.

Quick answer

Motor full-load amps for circuit sizing come from NEC Table 430.248 (single-phase) or Table 430.250 (three-phase), not the nameplate: a 10 HP, 460 V three-phase motor is 14 A and a 1 HP, 230 V single-phase motor is 8 A. Conductors are sized at 125% of that current (430.22) and an inverse-time breaker at up to 250% (430.52), rounded up to the next standard size.

Examples

Motor	NEC FLA	125% conductor (75 °C Cu)	250% breaker
1 HP, 230 V, 1-phase	8 A	10 A → 14 AWG	20 A
5 HP, 230 V, 1-phase	28 A	35 A → 10 AWG	70 A
5 HP, 208 V, 3-phase	16.7 A	20.9 A → 12 AWG	45 A
10 HP, 230 V, 3-phase	28 A	35 A → 10 AWG	70 A
10 HP, 460 V, 3-phase	14 A	17.5 A → 14 AWG	35 A
50 HP, 460 V, 3-phase	65 A	81.3 A → 4 AWG	175 A

Pick phase and voltage, enter HP or kW, and add the nameplate amps to get the overload setting too.

Summary