A motor current chart is a lookup table, not a calculation. Find the motor's horsepower in the left column, then read across to the column that matches your supply voltage. The number you land on is the full‑load current in amps.
Find the motor's horsepower in the left column, then read across to the column that matches your supply voltage. The number you land on is the full‑load current in amps.
At 230 V three‑phase, motors draw roughly 2.5 amps per horsepower. A 10 hp, 230 V motor draws about 28 amps.
At 460 V three‑phase, motors draw roughly 1.25 amps per horsepower — half the 230 V figure. A 10 hp, 460 V motor draws about 14 amps.
The chart works because the code assigns standard full‑load current values to each horsepower and voltage rating. A 10 hp, 460 V motor draws 14 amps at full load; a 10 hp, 230 V motor draws 28 amps. Double the voltage and the current halves, which is why a motor rated for a higher voltage uses a thinner conductor for the same horsepower.
Rule of thumb for 575 V: roughly 1 amp per horsepower. These are approximations. The table below is the precise reference, and you should use the table for any sizing decision rather than the rule of thumb.
Locate the motor's horsepower in the left column, then read across to the voltage column that matches your supply.
A 10 hp motor draws 28 A at 230 V but only 14 A at 460 V. Double the voltage halves the current.
2.5 A/hp at 230 V, 1.25 A/hp at 460 V, and 1 A/hp at 575 V are useful checks — but always use the table for final sizing.
Full‑load amps determine conductor size, breaker rating, contactor selection, and the generator kVA needed to start the motor.
The table below lists full‑load current in amps for three‑phase squirrel‑cage induction motors, from 1/2 through 200 horsepower, across the four common supply voltages. Values are from NEC Table 430.250.
| HP | 208 V | 230 V | 460 V | 575 V |
|---|---|---|---|---|
| 1/2 | 2.2 A | 2.0 A | 1.0 A | 0.8 A |
| 3/4 | 3.1 A | 2.8 A | 1.4 A | 1.1 A |
| 1 | 4.0 A | 3.6 A | 1.8 A | 1.4 A |
| 1-1/2 | 5.7 A | 5.2 A | 2.6 A | 2.1 A |
| 2 | 7.5 A | 6.8 A | 3.4 A | 2.7 A |
| 3 | 10.6 A | 9.6 A | 4.8 A | 3.9 A |
| 5 | 16.7 A | 15.2 A | 7.6 A | 6.1 A |
| 7-1/2 | 24.2 A | 22 A | 11 A | 9 A |
| 10 | 30.8 A | 28 A | 14 A | 11 A |
| 15 | 46.2 A | 42 A | 21 A | 17 A |
| 20 | 59.4 A | 54 A | 27 A | 22 A |
| 25 | 74.8 A | 68 A | 34 A | 27 A |
| 30 | 88 A | 80 A | 40 A | 32 A |
| 40 | 114 A | 104 A | 52 A | 41 A |
| 50 | 143 A | 130 A | 65 A | 52 A |
| 60 | 169 A | 154 A | 77 A | 62 A |
| 75 | 211 A | 192 A | 96 A | 77 A |
| 100 | 273 A | 248 A | 124 A | 99 A |
| 125 | 343 A | 312 A | 156 A | 125 A |
| 150 | 396 A | 360 A | 180 A | 144 A |
| 200 | 528 A | 480 A | 240 A | 192 A |
| HP | 230 V | 460 V | 575 V |
|---|---|---|---|
| 250 | 604 A | 302 A | 242 A |
| 300 | 722 A | 361 A | 289 A |
| 350 | 828 A | 414 A | 336 A |
| 400 | 954 A | 477 A | 382 A |
| 450 | 1030 A | 515 A | 412 A |
| 500 | 1180 A | 590 A | 472 A |
Locate the motor's horsepower in the left column, then read across to your supply voltage. That is the full‑load current.
A 100 hp motor draws 248 A at 230 V but only 124 A at 460 V. Double the voltage halves the current.
Full‑load amps determine every downstream component — from conductor size to starter rating to generator kVA.
Large motors are almost always run at 230, 460, or 575 V. The code omits 208 V for motors above 200 HP.
A 500 hp motor draws 590 amps at full load. This is a serious load — conductor, switchgear, and generator sizing all follow from this number.
Not every motor load is three‑phase. Single‑phase motors appear on pumps, fans, compressors, and small machine tools, and they have their own full‑load current table. The single‑phase motor current chart below covers 1/6 through 10 horsepower.
| HP | 115 V | 208 V | 230 V |
|---|---|---|---|
| 1/6 | 4.4 A | 2.4 A | 2.2 A |
| 1/4 | 5.8 A | 3.2 A | 2.9 A |
| 1/3 | 7.2 A | 4.0 A | 3.6 A |
| 1/2 | 9.8 A | 5.4 A | 4.9 A |
| 3/4 | 13.8 A | 7.6 A | 6.9 A |
| 1 | 16 A | 8.8 A | 8.0 A |
| 1-1/2 | 20 A | 11 A | 10 A |
| 2 | 24 A | 13.2 A | 12 A |
| 3 | 34 A | 18.7 A | 17 A |
| 5 | 56 A | 30.8 A | 28 A |
| 7-1/2 | 80 A | 44 A | 40 A |
| 10 | 100 A | 55 A | 50 A |
This is the most common point of confusion in motor circuit design, and it is worth getting right. A motor carries two current ratings, and they serve different purposes.
Comes from the chart. Use it to size the conductors, disconnect, short‑circuit and ground‑fault protection, and the breaker or fuse. This is the code rule: NEC 430.6(A)(1) requires you to use the table value, not the nameplate, for these components.
Stamped on the motor. Use it only to select the overload protection, which protects the motor windings themselves. The nameplate value is the actual measured current for that specific motor from that specific manufacturer.
Motors of the same horsepower and voltage vary slightly from one manufacturer to another. The table value is conservative enough to cover all of them. Using the nameplate value for the conductor can undersize the circuit if a replacement motor draws slightly more.
Once you have the FLC from the chart, size the conductor at 125% of FLC under NEC 430.22 for continuous duty. A 10 hp, 460 V motor draws 14 amps, so the conductor is sized for 17.5 amps minimum.
The breaker or fuse is sized from FLC using the multipliers in NEC 430.52: up to 250% for inverse‑time breakers, 175% for time‑delay fuses, or 300% for non‑time‑delay fuses.
The chart is where it all starts. Conductor, breaker, contactor, and overload each branch off that one full‑load current number.
Full‑load current leads directly to the generator question, because a motor's starting current, not its running current, is what a generator must survive. A motor draws four to eight times its full‑load current for the first few seconds of start‑up.
A 50 hp, 460 V motor runs at 65 amps but can demand 300 to 500 amps momentarily as it comes up to speed. The generator must be sized to start that motor without excessive voltage dip.
Start from the motor's apparent power in kVA: kVA = √3 × V × A ÷ 1000 A 50 hp, 460 V motor at 65 amps draws about 52 kVA at full load. Its starting demand is far higher, which is why generator sizing uses motor starting kVA, not running kVA.
A 50 hp, 460 V motor has a full‑load current of 65 A from the NEC table. Running kVA = √3 × 460 × 65 ÷ 1000 = ~52 kVA. At start‑up, the motor draws ~5× FLC = 325 A, requiring ~260 kVA for the first few seconds. A generator sized for the running load would be undersized by a factor of 5. The generator must be selected to handle the starting surge — which is why our generator sizing calculator always includes motor start‑up demand.
If the load is a motor, the chart is the first step and the generator is the last. Get the full‑load current right, and everything downstream falls into place.
Shandong Huali Electromechanical Co., Ltd. manufactures diesel generator sets, dust-suppression equipment, and industrial automation systems, with over 25 years of experience and exports to more than 20 countries. We publish free electrical reference tools to help engineers and buyers specify power systems correctly.
A: It depends on horsepower and voltage. A 10 hp, 460 V motor draws 14 amps at full load; a 10 hp, 230 V motor draws 28 amps. Use this 3 phase motor current chart to look up the full-load current for any horsepower and voltage combination.
A: Find the horsepower in the left column, then read across to the voltage column that matches your supply. The value is the full-load current in amps. Confirm the value is reasonable with the rule of thumb: about 2.5 amps per horsepower at 230 V and 1.25 amps per horsepower at 460 V.
A: Table full-load current (FLC) is the code-assigned value from NEC 430.250. Use it to size conductors, breakers, fuses, and disconnects. Nameplate full-load amps (FLA) is the manufacturer’s rating, and you use it only for overload protection. The code requires the table value for the branch circuit under NEC 430.6(A)(1).
A: Table full-load current (FLC) is the code-assigned value from NEC 430.250. Use it to size conductors, breakers, fuses, and disconnects. Nameplate full-load amps (FLA) is the manufacturer’s rating, and you use it only for overload protection. The code requires the table value for the branch circuit under NEC 430.6(A)(1).
A: A 10 hp three-phase motor draws 28 amps at 230 V, 14 amps at 460 V, and 11 amps at 575 V. At 208 V it draws 30.8 amps.
A: Start with the full-load current from the chart, then size the conductor at 125% of that value for continuous duty under NEC 430.22. A 10 hp, 460 V motor at 14 amps needs a conductor sized for at least 17.5 amps, which lands on 14 AWG copper at 75°C.
A: NEC Table 430.250 is the National Electrical Code table of full-load current for three-phase alternating-current motors. It assigns a standard full-load current to each horsepower and voltage rating and is the reference used to size motor branch circuits.
A: For an approximate value, use 2.5 amps per horsepower at 230 V or 1.25 amps per horsepower at 460 V. For an exact value, use I = hp × 746 ÷ (√3 × V × efficiency × power factor). Our motor amps calculator runs this formula with your actual efficiency and power factor.
