How Many Amps Does a 1/4 HP single-phase Motor Draw at 208V?

1/4 HP single-phase motor at 208V draws 1.24 amps. Single-phase motors are the standard for residential applications and small equipment. The amp draw depends on voltage, motor efficiency, and power factor.

Typical 1/4 HP motor applications: small pool pumps, light-commercial fans, booster pumps.

1/4 HP single-phase motor at 208V

1.24 Amps running

Calculated running current at the motor terminals at the assumed 85% efficiency and PF 0.85. This is a conversion from the nameplate horsepower using those assumptions, not a measured value; a real meter reading depends on the motor's actual nameplate efficiency, loading, temperature, and motor design.

NEC Table 430.248 FLC (code sizing base)3.2 A

Conductor min ampacity (NEC 430.22, 125% of FLC)4 A

Electrical input (HP × 746 ÷ efficiency)219.41 W

Try: 1/3HP at 208V 1/6HP at 208V 1/8HP at 208V 1/2HP at 208V

Volts

Motor Type

Running Amps (meter)

1.24

NEC Table 430.248 FLC (code sizing)

3.2

Use the running amps for metering and energy calculations. For branch-circuit sizing, AC motors use the NEC Table 430.248 / 430.250 full-load current under NEC 430.6(A)(1); DC motors use the motor nameplate full-load current under NEC 430.6(A)(3), with Table 430.247 as the reference. Three-phase current is shown per line on a balanced circuit.

Formula (single-phase)

I_(A) = (HP × 746) ÷ (V × Eff × PF)

(1/4 × 746) ÷ (208 × 0.85 × 0.85) = 186.5 ÷ 150.28 = 1.24 A

Convert HP to watts: 1/4 × 746 = 186.5W
Denominator: 208 × 0.85 × 0.85 = 150.28
Result: 186.5 ÷ 150.28 = 1.24 amps

NEC Reference Values

This section lists the Code reference numbers a motor branch circuit is sized from. Final conductor, breaker, disconnect, and overload selection is an install decision a licensed electrician makes against the motor nameplate, the actual install conditions, and the applicable NEC articles, not a decision a conversion page can make for you.

NEC Sizing Base: NEC Table 430.248 FLC

Per NEC 430.6(A)(1), motor branch-circuit conductors, switches, and overcurrent protection are sized from the values in Table 430.248 (single-phase) or Table 430.250 (three-phase), not from the motor nameplate and not from a calculated full-load amps. For a 1/4 HP single-phase motor at 208V, the table value is 3.2 A (the 115V column covers 110-120V systems under 430.6(A)(1)).

The 1.24 A shown in the hero is the calculated running current at 85% efficiency and PF 0.85. This is a conversion from the nameplate horsepower under those assumptions, not a measured value; a real meter reading depends on the motor's actual efficiency, loading, temperature, and design. Use this figure for energy and metering estimates, and use 3.2 A as the reference FLC when an electrician walks through NEC 430 against the nameplate.

NEC 430.22 Conductor Rule (reference formula)

NEC 430.22 requires motor branch-circuit conductor ampacity of at least 125% of the Code sizing FLC. As a reference calculation against the NEC Table 430.248 value: 3.2 × 1.25 = 4 A. The selected conductor is taken from NEC Table 310.16 at the applicable termination temperature column, with ambient, bundling, and cable-type adjustments applied by the installer. Motor branch-circuit conductors are exempt from the 240.4(D) small-conductor rule via 240.4(G).

NEC 430.52 Overcurrent Protection (code caps)

NEC Table 430.52(C)(1) gives the maximum rating for motor short-circuit and ground-fault protection as a percentage of the Code sizing FLC. The percentage depends on the device type:

Device Type	Maximum % of Table FLC (430.52(C)(1))
Non-time-delay fuse	300%
Dual-element (time-delay) fuse	175%
Inverse-time circuit breaker	250%
Instantaneous-trip circuit breaker	800%

These percentages are maximum caps, not install picks. A real circuit applies the percentage against the Code sizing FLC for the specific device type, rounds up to a standard size per 430.52(C)(1)(a), and is verified against the motor nameplate and the install conditions by the installer. The elevated percentages exist so short-circuit protection does not nuisance-trip on locked-rotor startup inrush.

Locked Rotor (Startup) Current

During the first 2-5 seconds of startup, a squirrel-cage induction motor typically draws 5 to 7 times the NEC Table 430.248 FLC of 3.2 A (roughly 16 to 22.4 A). This is why the 430.52(C)(1) percentages above are so much higher than running current: the short-circuit/ground-fault protective device has to ride through locked-rotor inrush without tripping. Actual LRA is set by the motor's NEMA code letter on the nameplate and should be checked there for a real install.

Current	Amps	Duration
Calculated running current (meter)	1.24 A	Continuous at full load
NEC Table 430.248 FLC (Code reference)	3.2 A	Sizing base, not metered
Locked rotor (typical, 5-7×)	16-22.4 A	2-5 seconds

Operating Cost

Motor mechanical output is 186.5 W (1/4 HP × 746). Electrical input at the terminals is higher because no motor is 100% efficient: 186.5 ÷ 0.85 = 219.41 W. At $0.17/kWh, running cost is $0.04/hour or $8.95/month at 8 hours/day. Full breakdown at 219.41 W.

Amps by Motor Efficiency (single-phase)

Motor efficiency directly affects amp draw. A more efficient motor draws less current for the same HP output. Values below are the calculated single-phase running current at 208V and PF 0.85:

Efficiency	Amps at 208V	Watts Consumed	Waste Heat
75%	1.41 A	248.67 W	62.17 W
80%	1.32 A	233.13 W	46.63 W
85%	1.24 A	219.41 W	32.91 W
90%	1.17 A	207.22 W	20.72 W
95%	1.11 A	196.32 W	9.82 W

Other HP Values at 208V (single-phase)

Running current is the calculated single-phase draw at 85% efficiency and 0.85 PF (a conversion from HP under those assumptions, not a measured value). NEC Table FLC is the value from NEC Table 430.248 used for branch-circuit conductor and OCP sizing under NEC 430.6(A)(1). LRA is estimated at 5-7× the NEC table FLC; rows outside the table show n/a because there is no code-authoritative LRA basis for that HP/voltage/phase combination. Row links open each result page in single-phase mode.

HP	Running Amps (calculated)	NEC Table 430.248 FLC	LRA Estimate (5-7× FLC)
1/8 HP	0.6205 A	off-table	n/a
1/6 HP	0.8275 A	2.4 A	12-16.8 A
1/4 HP	1.24 A	3.2 A	16-22.4 A
1/3 HP	1.65 A	4 A	20-28 A
1/2 HP	2.48 A	5.4 A	27-37.8 A
3/4 HP	3.72 A	7.6 A	38-53.2 A
1 HP	4.96 A	8.8 A	44-61.6 A
1.5 HP	7.45 A	11 A	55-77 A
2 HP	9.93 A	13.2 A	66-92.4 A
3 HP	14.89 A	18.7 A	93.5-130.9 A
5 HP	24.82 A	30.8 A	154-215.6 A
7.5 HP	37.23 A	44 A	220-308 A
10 HP	49.64 A	55 A	275-385 A
15 HP	74.46 A	off-table	n/a
20 HP	99.28 A	off-table	n/a
25 HP	124.1 A	off-table	n/a
30 HP	148.92 A	off-table	n/a
40 HP	198.56 A	off-table	n/a
50 HP	248.2 A	off-table	n/a
75 HP	372.31 A	off-table	n/a

Same HP, Other Voltages (single-phase)

speed 1/4 HP at 120V = 2.15A speed 1/4 HP at 220V = 1.17A speed 1/4 HP at 230V = 1.12A speed 1/4 HP at 240V = 1.08A speed 1/4 HP at 400V = 0.6453A speed 1/4 HP at 480V = 0.5378A

Related Calculations

bolt 219W electrical input to amps at 208V payments 219W running cost cable Wire size for 4A at 208V (NEC 430.22 minimum: 125% of 3.2A NEC Table 430.248 FLC)

Frequently Asked Questions

How many amps does a 1/4 HP single-phase motor draw at 208V?expand_more

At the terminals, a 1/4 HP single-phase motor at 208V draws about 1.24 amps at 85% efficiency and 0.85 power factor. For NEC branch-circuit sizing use the NEC Table 430.248 full-load current instead: 3.2 A.

What does NEC 430.52(C)(1) say about OCP for a 1/4 HP single-phase motor?expand_more

NEC Table 430.52(C)(1) gives the maximum OCP rating as a percentage of the NEC Table 430.248 FLC. The ceilings by device type are 300% for non-time-delay fuses, 175% for dual-element (time-delay) fuses, 250% for inverse-time circuit breakers, and 800% for instantaneous-trip breakers. These percentages are ceilings, not starting points, and 250% is not a blanket motor rule. The actual max for a specific install comes from picking the device type, applying the matching percentage to the 3.2 A NEC Table 430.248 FLC, rounding up to a standard size per 430.52(C)(1)(a), and verifying against the motor startup profile.

How much does a 1/4 HP motor cost to run?expand_more

Operating cost is based on electrical input, not mechanical HP output. At 85% efficiency, a 1/4 HP motor draws about 219.41 W at the terminals. At $0.17/kWh (US residential average, last reviewed April 2026), that is $0.04/hour or $8.95/month at 8 hours/day.

What branch-circuit context does a 1/4 HP single-phase motor at 208V typically sit in?expand_more

At 208V single-phase, motor branches are dedicated circuits, not general-purpose receptacles. Common NEMA configurations at this voltage are the 6-series (6-15, 6-20, 6-30, 6-50) and the 14-series (14-30, 14-50) when a neutral is needed, sized to the motor branch-circuit OCP the installer picks under NEC 430.52(C)(1). The NEC Table 430.248 FLC of 3.2 A is the reference number an electrician feeds into 430.22 and 430.52, not a receptacle pick on its own. Verify against the nameplate and local code.

What is locked rotor amps for a 1/4 HP single-phase motor?expand_more

Locked-rotor (startup) current typically runs 5-7 times the NEC Table 430.248 FLC for a squirrel-cage induction motor: 16-22.4 A for 2-5 seconds. The exact value depends on the NEMA code letter stamped on the motor nameplate.

This calculator provides estimates for reference purposes only. Always consult a licensed electrician and verify compliance with the National Electrical Code (NEC) and local electrical codes before performing any electrical work.