Motor full-load current tables provide reference amperes for a specified motor horsepower, phase, and rated voltage. Select the matching row and voltage column, then confirm that the table applies to the motor and the calculation being performed. A table value is not necessarily the motor’s nameplate current or the current it draws in service. Those values serve different purposes.
The reference values below are NEC-based, not universal motor ratings or IEC sizing data. Their underlying sources identify NEC Tables 430.248 and 430.250; the manufacturer selection sheet identifies the 2020 NEC as its reference. These are selected reference entries, not a reproduction of every voltage, horsepower, motor category, or table note. Confirm the edition adopted for the project and its applicable provisions before using a reference current in a code calculation.
Single-Phase Motor Full-Load Current Table
Use the single-phase table only for an applicable single-phase AC motor. Horsepower represents rated mechanical output, and every current entry is in amperes.
The following entries are drawn from the motor-current columns in US Breaker’s Motor Application—Sizing & Selection by Hp sheet and Littelfuse’s Motor Protection Basics application guide, published in 2015. Both identify NEC Table 430.248 as the basis for single-phase current values. The sources are manufacturer references, not the complete adopted code text.
| Motor output, hp | 115 V, A | 230 V, A |
|---|---|---|
| 1/6 | 4.4 | 2.2 |
| 1/4 | 5.8 | 2.9 |
| 1/3 | 7.2 | 3.6 |
| 1/2 | 9.8 | 4.9 |
| 3/4 | 13.8 | 6.9 |
| 1 | 16 | 8 |
| 1 1/2 | 20 | 10 |
| 2 | 24 | 12 |
| 3 | 34 | 17 |
| 5 | 56 | 28 |
| 7 1/2 | 80 | 40 |
| 10 | — | 50 |
Sources: US Breaker, Motor Application—Sizing & Selection by Hp, single-phase tables; Littelfuse, Motor Protection Basics, printed page 9. A dash means the entry is not reproduced here, not that the motor rating is unavailable or prohibited.
For example, a 5 hp single-phase motor has a listed reference current of 28 A in the 230 V column. The same horsepower does not identify the same current in a three-phase table.
Three-Phase Motor Full-Load Current Table
These entries apply to the induction-type squirrel-cage and wound-rotor motor category identified in the source’s reference to NEC Table 430.250. They are line currents, not internal winding currents. Do not divide them by three or apply another (\sqrt{3}) factor after looking them up.
| Motor output, hp | 208 V, A | 230 V, A | 460 V, A |
|---|---|---|---|
| 1/2 | 2.4 | 2.2 | 1.1 |
| 3/4 | 3.5 | 3.2 | 1.6 |
| 1 | 4.6 | 4.2 | 2.1 |
| 1 1/2 | 6.6 | 6.0 | 3.0 |
| 2 | 7.5 | 6.8 | 3.4 |
| 3 | 10.6 | 9.6 | 4.8 |
| 5 | 16.7 | 15.2 | 7.6 |
| 7 1/2 | 24.2 | 22 | 11 |
| 10 | 30.8 | 28 | 14 |
| 15 | 46.2 | 42 | 21 |
| 20 | 59.4 | 54 | 27 |
| 25 | 74.8 | 68 | 34 |
| 30 | 88 | 80 | 40 |
Source: US Breaker, Motor Application—Sizing & Selection by Hp, 208 V, 230 V, and 460 V tables, explicitly based on NEC Table 430.250 (2020). Only its reference-current data are reproduced here; its contactor, overload-relay, and breaker selections are not included.
For a 10 hp three-phase motor, the table gives 30.8 A at 208 V, 28 A at 230 V, and 14 A at 460 V. These are separate lookup entries. Use the listed 208 V value rather than substituting a 200 V value or scaling the 230 V entry.
Match the Motor and Voltage Before Looking Up Current
Collect the following information from the motor nameplate and project documents:
- Motor phase and type.
- Rated shaft horsepower.
- Rated voltage and the connection actually being used.
- Rated speed and whether the motor is multispeed or has unusual torque characteristics.
- The required calculation and its governing code edition, where applicable.
The distinction between ordinary and special motor applications matters. The 2023 NEC text reproduced in Eaton’s code-change publication distinguishes low-speed motors below 1,200 rpm, high-torque motors, and multispeed motors from the general table-value rule. An ordinary horsepower-and-voltage lookup should not be assumed to resolve those applications.
Motor voltage is not always the nominal system voltage
A 460 V motor rating and a nominal 480 V supply designation are not contradictory. NEC motor-table notes permit specified reference currents to be used over stated system-voltage ranges, including 440–480 V for the 460 V column and 220–240 V for the 230 V column. This is a permitted table-use convention—not a claim that actual motor current remains constant throughout those ranges. Confirm the notes in the adopted edition.
Similarly, do not treat the 200 V and 208 V columns as interchangeable. Manufacturer charts sometimes group motors by supply-system voltage while presenting a particular motor-voltage reference. Read both the heading and the source notes rather than choosing the nearest-looking number.
Missing horsepower or voltage requires another source
If a rating is absent from these excerpts, obtain the relevant complete table or the motor manufacturer’s data. A missing entry is not permission to interpolate, round horsepower down, or scale a current inversely with voltage for a code calculation.
If the motor is marked only in output kW, establish the applicable horsepower rating or accepted calculation basis before selecting a row. An electrical input-kW measurement is not the motor’s rated shaft output and cannot be substituted directly for it.
Table FLC, Nameplate Current, and Operating Current
The decisive distinction is the current’s basis, not whether a document labels it “FLC,” “FLA,” or simply “amps.”
| Current value | What it represents | Appropriate use |
|---|---|---|
| Table full-load current | A standardized reference selected by motor category, horsepower, and voltage | Calculations that specifically require the applicable table value |
| Nameplate current | The manufacturer’s rated current for the identified motor and rating conditions | Motor-specific comparisons and calculations requiring nameplate current |
| Estimated operating current | A calculated current based on assumed or documented shaft load, efficiency, power factor, and voltage | Preliminary load comparisons under the stated assumptions |
| Measured operating current | Current observed during a particular operating condition | Evaluation of that recorded condition—not automatic replacement of a required table or nameplate value |
The table-versus-nameplate distinction is established in the NEC motor-current provisions; operating current also depends on the actual load and operating voltage.
When the table value is the required input
For general motor applications, the 2023 NEC wording reproduced by Eaton identifies table values rather than actual nameplate current for determining conductor ampacity, switch current ratings, and branch-circuit short-circuit and ground-fault protection ratings, subject to the provision’s exclusions and exceptions. A lower nameplate current therefore does not automatically justify reducing those calculated values.
This requirement must be applied within the project’s adopted rules. It does not make NEC table currents the correct input for every motor calculation or for an installation governed by another standards system.
When nameplate current matters
Motor overload protection is a different task from branch-circuit short-circuit and ground-fault protection. The nameplate current is the normal starting input for separate overload-device calculations under the cited NEC framework. The applicable overload method, service factor, temperature-rise marking, device instructions, and exceptions still determine how that input is used. Do not select an overload setting merely by copying the reference-current column.
For a dual-voltage motor, use the nameplate current corresponding to the actual voltage and connection. Keep service-factor amperes, if separately marked, distinct from rated full-load amperes.
What measured current can—and cannot—show
A partially loaded motor may draw less than its nameplate full-load current. It still draws current at no mechanical load, so a reading equal to 50% of nameplate current does not establish 50% shaft loading.
For a useful operating record, retain the voltage, load condition, speed, and whether the reading was taken during starting or steady operation. For three-phase equipment, retain the individual phase-current readings rather than only an average. An operating measurement describes those conditions; it does not, by itself, establish a new motor rating or replace a prescribed design-current basis.
Why a Horsepower Calculation May Not Match the Table
A current estimate can be reconstructed from mechanical output power and electrical input relationships. Using (746\ \text{W/hp}), the single-phase relationship is:
[
I_{\text{est}}=\frac{746H}{V\eta PF}
]
For a balanced three-phase supply:
[
I_{\text{est}}=\frac{746H}{\sqrt{3},V_{LL}\eta PF}
]
Where:
- (I_{\text{est}}) is estimated line current in amperes.
- (H) is shaft output at the evaluated operating point, in horsepower.
- (V) is the voltage across the single-phase load, in volts.
- (V_{LL}) is three-phase line-to-line voltage, in volts.
- (\eta) is motor efficiency as a decimal.
- (PF) is power factor as a decimal.
Eaton publishes these horsepower-to-current relationships in its electrical-formula reference. Efficiency and power factor must correspond to the operating point being estimated; use 0.90 for 90% efficiency, not 90.
These equations require positive voltage, (0<\eta\leq1), and (0<PF\leq1). A zero or missing efficiency or power factor does not produce a valid estimate. The balanced three-phase equation also does not calculate individual phase currents for an unbalanced condition.
Example: 10 hp at 460 V
Assume a three-phase motor delivers 10 hp at 460 V line-to-line, with 90% efficiency and 0.85 power factor. These are illustrative assumptions, not verified data for a particular motor.
[
I_{\text{est}}
=
\frac{746\times10}
{\sqrt{3}\times460\times0.90\times0.85}
\approx12.2\ \text{A}
]
The reference table lists 14 A for a 10 hp, 460 V three-phase motor. The estimated 12.2 A does not invalidate the 14 A reference: the calculation uses assumed efficiency and power factor, while the table provides a standardized current for a different purpose. Neither result establishes the current of an unidentified motor.
Do not multiply table FLC by an additional efficiency or power-factor correction to make it agree with this estimate. Select the current basis required by the task.
Carry the Correct Current Into the Next Calculation
Record a lookup with enough information to reproduce it. For example:
“10 hp, three-phase induction motor; 460 V reference column; 14 A; NEC Table 430.250 (2020) as reproduced in the US Breaker selection sheet.”
That record identifies a reference current—not a conductor size, protective-device rating, or measured load.
If a subsequent calculation calls for 125% of that confirmed current, the arithmetic is:
[
I_{\text{target}}=1.25\times14=17.5\ \text{A}
]
Here, 17.5 A is a conditional ampacity target. Whether that factor applies must be established from the motor duty and governing provisions. Selecting an actual conductor still requires the applicable ampacity data, terminal-temperature limitations, correction and adjustment factors, and other installation requirements. The result is not a 17.5 A breaker selection.
Use the existing Sizing Calculator tools according to their stated input basis:
- Motor Operating Current Estimate estimates single-phase or three-phase current from entered shaft horsepower, efficiency, power factor, and voltage. Its stated purpose is an operating-current estimate, not NEC table FLC.
- Motor Branch Conductor Minimum Ampacity Arithmetic provides the next arithmetic step for a motor branch-conductor check. Establish the required current basis from the applicable rules before carrying a value into that calculation.
- Motor Overload Setting Arithmetic specifically calls for motor nameplate current; do not substitute a table value unless the applicable rules and device instructions permit it.
Keep the current source attached to the result as it moves between calculations. A table lookup, a nameplate rating, and an operating-current estimate may all be valid numbers while remaining unsuitable substitutes for one another.