Amp to Wire Size Calculator

Created by Arturo Barrantes
Reviewed by Wojciech Sas, PhD
Last updated: May 18, 2022

The Amp to wire size calculator will help you determine the appropriate electrical wire for your new connection. Keep reading to find out how to size your cables.

How to calculate the wire size based on the system amperes?

The following information is required before we start:

  • The amperage at which your system will run: It can be direct current or alternate current (single-phase or three phases).
  • System configuration: Single-phase / Three-phase.
  • The system voltage.
  • Wire size material since it affects the electrical resistivity.
  • Distance between your energy source and the equipment you want to energize.
  • Allowed voltage drop per the equipment requirements.

Once we have it all, we will use the following formula:

A=2×IϱL×ϕV×%drop,\quad A = \frac{2\times I \varrho L \times \phi}{V \times \%\text{drop}},


  • %drop\%\text{drop} — Allowable voltage drop, in %.
  • VV — Source voltage, measured in volts.
  • II — System current, measured in amperes.
  • ϱ\varrho — Resistivity of the conductor material, measured in ohmmeters;
  • LL — Length of the wire, measured in meters; and
  • ϕ\phi — Phase factor, 1 for DC / AC single phase and 3/2\sqrt{3}/2 for AC three-phase.
  • AA — Cross-sectional wire area measured in square meters.

The result will be expressed in mm² (if using the metric system).

It is common for wires to indicate their size in AWG (American Wire Gauge) units. Do not worry; our Amp to wire size calculator also provides results in AWG.

How do you use this amp to wire size calculator?

To find the desired wire size:

  1. Verify your connection: DC or AC single/three-phase.
  2. Specify the voltage source and define the system amperage.
  3. Define the wire material you will use, the operating temperature, and the voltage drop.
  4. Finally, input the length of your cable (remember, it's a one-way distance).

As a result, the Amp to wire size calculator will indicate the cross area of the cable you need to install.

Other useful tools like the amp to wire size calculator

Since you already know how to size a wire based on the required amperes in the system, you can take a look at other calculators:


How do I calculate amp wire size?

You can use Omnicalculator's Amp to wire size tool or do the following:

  1. For AC single phase: Get the amperage of your system, one-way length of the cables you want to install, and wire material resistivity.
  2. Multiply all the above values and multiply the result by two.
  3. Divide the previous result by the voltage drop in the system.
  4. The final result represents the cable area you need. Now go to an AWG chart and select your cable.

What size wire can handle amps?

The answer depends on the following variables:

  • System amperage and voltage.
  • Distance between feeder and equipment.
  • Wire material.

We recommend you check the Omnicalculator's Amp to wire size calculator for a direct result.

Arturo Barrantes
Specify the system's current and the other electrical variables:
Current (I)
Electrical system
DC/AC Single-phase
Source voltage
Allowable voltage drop (V)
Conductor material
One-way distance (D)
Maximum wire temperature
Recommended wire size
Wire cross-sectional area (A)
Wire gauge
Wire diameter (d)
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