Perform fast calculations with our user-friendly online calculator! Conveniently crunch numbers and solve equations instantly. Ideal for quick math tasks, our tool simplifies your daily computations effortlessly. Try our intuitive calculator for accurate results on the go!
Calculate motor wire size fast with our motor wire size calculator. Find motor FLC, required ampacity, and wire gauge for single and 3-phase motors.
Choosing the right wire is key for a safe motor circuit. A wire that's too small can overheat. A wire that's too large can add cost.
Our motor wire size calculator makes this job quick. It uses the motor phase, voltage, horsepower, wire material, and temperature rating. It then finds the motor's full-load current (FLC), applies the 125% sizing factor, and selects a wire with enough ampacity.
This tool works as an electric motor wire size calculator for both single-phase and 3-phase motors. It can also help with motor cable size and motor conductor sizing.
The main formula used by this calculator is:
Motor required ampacity = Motor FLC × 1.25
Here, FLC means full-load current.
The calculator gets FLC from its built-in NEC motor tables. It uses NEC Table 430.248 for single-phase motors and NEC Table 430.250 for three-phase motors.
After finding FLC, the calculator checks the conductor ampacity table.
Wire size is selected when:
Wire ampacity ≥ Required ampacity
The calculator picks the smallest listed wire that meets this value.
For example, if the motor FLC is 22 A:
Required ampacity = 22 × 1.25 = 27.5 A
A 10 AWG copper wire with a 75°C ampacity of 35 A meets this value.
So the calculated wire size is 10 AWG copper.
Using our motor wire sizing calculator is simple.
Let's use a 7.5 HP, 230 V, three-phase motor with copper wire at 75°C.
The calculator finds the motor FLC from its three-phase table:
FLC = 22 A
Now apply the motor wire size formula:
Required ampacity = 22 × 1.25
Required ampacity = 27.5 A
Next, compare this value with the copper wire ampacity table.
12 AWG copper = 25 A, which is too low.
10 AWG copper = 35 A, which is enough.
Therefore:
Motor wire size = 10 AWG copper
Required ampacity = 27.5 A
Wire ampacity = 35 A
This is the core calculation performed by our 3 phase motor wire size calculator.
Our motor wire size calculator gives you a fast way to estimate the conductor size for supported motor combinations. It uses table-based motor FLC values, applies the 125% factor, and matches the result with conductor ampacity.
It can help with motor wire gauge, motor cable sizing, and motor conductor size calculations.
Keep in mind that real installations may need additional checks. Voltage drop, ambient temperature, conductor adjustment, installation method, terminals, and local electrical rules can affect the final wire choice. A motor breaker size calculator is also a separate calculation and should not be confused with conductor sizing.
A motor wire size calculator finds the required conductor ampacity and selects a suitable wire size based on motor FLC and conductor ampacity.
The core formula is:
Required ampacity = FLC × 1.25
First find the motor FLC from the applicable motor table. Multiply FLC by 1.25. Then select a conductor whose allowable ampacity meets or exceeds the result.
HP is used with motor voltage and phase to obtain the table-based FLC. The FLC then determines the required conductor ampacity.
This calculator is designed around the programmed NEC single-phase and three-phase AC motor tables. It does not calculate DC motor wire size.
No. Motor conductor sizing and motor breaker sizing are separate calculations. A breaker must account for motor circuit protection rules, while the conductor calculation determines the required wire ampacity.