WireGaugeCalc Free calculator · NEC cited · works offline
40 Hp Motor Amps
40 hp motor amps is quick with WireGaugeCalc, which pulls the NEC full-load current value for your voltage and phase instead of a back-of-envelope guess.
You pick the horsepower, voltage, and whether it is single or three phase, so the calculator returns the table FLA used for sizing.
That FLA is the starting point for conductor ampacity and overload protection.
Open the calculatorEnter any two values and read the rest.
Ohm’s law: V = I × R and P = V × I. Field aid only, verify against the current NEC and your local authority having jurisdiction.
Reading the 40 Hp Motor FLA From the NEC Tables
The NEC sets motor full-load current in Table 430.250 for three-phase and Table 430.248 for single-phase, since motor nameplates vary.
For a 40 hp three-phase motor at 460V the table FLA is 52 amps, and the calculator shows the matching value for your voltage.
Conductor sizing uses 125% of that FLA because the motor is a continuous load.
Using the 40 Hp Motor FLA on the Job
The calculator gives you the numbers needed downstream:
- Table FLA for 200V, 230V, and 460V three-phase
- 125% of FLA for conductor ampacity
- A baseline for branch-circuit overload sizing
- Single-phase values when the motor is not three phase
- Clear amps so you can pick the wire size next
One app for every NEC calculation
WireGaugeCalc keeps the calculations you reach for most in one place:
- Voltage drop and wire sizing for any run
- Conduit fill for EMT, PVC, and RMC
- Box fill and junction box sizing
- Ampacity and temperature derating
- Motor circuit and load calculations
- Conduit bend offsets and saddles
Built for the field, works offline
The whole app runs on your phone, so it keeps working in a basement, an attic, or a job site with no signal.
There is no account to create and nothing to load. Open it, run the number, and get back to work.
- No signup and no signal needed
- Answers in a tap, not a spreadsheet
- Same tool on phone, tablet, and desktop
Every result cites the NEC article
Each answer shows the table or formula it came from, so you can check the method and learn the code as you go.
That makes the app useful on the job and during exam prep, since the reasoning is right next to the number.
Switch the code year your job runs on
Jurisdictions adopt the NEC at different times, so you can match the calculation to the code in force:
- NEC 2017, 2020, and 2023 tables
- Copper and aluminum conductors
- 60, 75, and 90 degree C terminations
- Single-phase and three-phase systems
Run the number, then get back to work
Stop flipping through a paper book or hopping between calculator sites. Enter your values, read the code-cited answer, and move on. Free to use, no signup.
Open the calculatorFrequently asked questions
Why use the NEC table FLA instead of the nameplate amps?
The NEC requires table values for sizing conductors and short-circuit protection, while the nameplate is used for overload protection. Always verify the values against the current NEC and your local authority having jurisdiction.
What is the FLA of a 40 hp motor at 460V?
A 40 hp three-phase motor at 460V has a table full-load current of 52 amps. The value rises at lower voltages, so the calculator adjusts when you change the voltage input.
Is WireGaugeCalc free to use?
Yes. Every calculator is free to run with no signup. A paid tier adds saved projects, PDF reports, and extra code years, but the core math stays free.
Does it work without internet?
Yes. The app runs on your device, so it keeps working with no signal on a job site, in a basement, or in an attic.
Are the results code accurate?
Results follow published NEC tables and standard formulas, and each answer shows the article it came from. It is a field aid, not a stamp of approval, so verify against the current code and your local authority before you wire anything.
Which NEC code year does it use?
You can switch between NEC 2017, 2020, and 2023, since jurisdictions adopt the code at different times. Pick the year your job runs on.