Wire Size & Voltage Drop Calc

Wire Size & Voltage Drop Calc by HeloStudios

Voltage Drop Calculator App for Android

Check voltage drop for single phase, split phase and balanced three phase circuits. Enter the load current, the one-way length and a copper conductor size in AWG or mm², and the app shows the drop in volts and percent, the voltage left at the load and the formula behind the result.

Get it on Google Play

  • Free to download, contains ads
  • Android 8.0 and newer
  • Calculations work offline
  • No account needed
App screen showing a 3.05% voltage drop, 6.35 V lost and 201.65 V at the load for a 208 V three phase circuit

What the app does

  • Voltage drop for three circuit types

    Single phase, split phase (line to line) or balanced three phase, from 1 to 2,000 V. Quick presets set 120, 240, 208, 480, 230 or 400 V, and you can type any other voltage.

  • AWG or mm², feet or metres

    Copper sizes from 14 AWG to 4/0 AWG or from 1.5 to 120 mm². Switching between feet and metres converts the length you entered.

  • Compare wire sizes

    Open the comparison under a result to see the same circuit with one thinner and two thicker sizes, on one shared scale with the 3% guideline marked. It compares voltage drop only.

  • AWG to mm² converter

    Convert an AWG size to its area in mm² and its nominal diameter, or find the smallest listed AWG size with at least the area you enter.

  • Copper ampacity reference

    The 60, 75 and 90 °C columns of NEC Table 310.16 for copper, 14 AWG to 4/0, with notes on the table conditions, small-conductor overcurrent limits and terminal ratings. No derating is applied.

  • Saved calculations

    Name and save results on your phone, then reopen, edit, rename, share or delete them. Shared and copied results always include the reference-only note.

Screens from the app

Real screens from version 1.3, with the numbers the app calculated.

  • Comparison for a 40 A, 120 ft, 208 V three phase circuit: 10 AWG 4.84%, 8 AWG 3.05%, 6 AWG 1.96% and 4 AWG 1.23% voltage drop
    Compare neighbouring wire sizes
  • Metric result for 400 V three phase, 32 A, 50 m and 6 mm²: 2.60% drop, 10.38 V lost and 389.62 V at the load
    Metric sizes: 400 V, 6 mm²
  • AWG to mm² converter showing 10 AWG as 5.261 mm² with a nominal diameter of 2.588 mm
    AWG to mm² converter
  • Copper ampacity table from NEC 310.16 with 60, 75 and 90 °C columns for 14 AWG to 4/0 AWG
    Copper ampacity reference
  • Saved calculations list with a 400 V voltage drop result and a 10 AWG to mm² conversion
    Saved calculations on the phone

How the voltage drop is calculated

The app uses a resistance-based reference model and shows the formula with your own numbers under every result.

VD = k × I × L × R ÷ 1000

%VD = VD ÷ V × 100

Voltage at the load = V − VD

k
2 for single phase and split phase; √3 (about 1.732) for balanced three phase.
I
Load current in amperes.
L
One-way length in feet or metres.
R
Copper conductor resistance at 75 °C, in ohms per 1000 ft (with feet) or per km (with metres).
V
Source voltage; line to line for split phase and three phase.

AWG resistance values come from NEC Chapter 9, Table 8 (DC resistance of uncoated copper at 75 °C). Metric values come from the IEC 60228 maximum resistance at 20 °C, corrected to 75 °C.

Worked example

208 V balanced three phase, 40 A, 120 ft one way, 8 AWG copper (R = 0.764 Ω per 1000 ft):

  • VD = √3 × 40 × 120 × 0.764 ÷ 1000 = 6.35 V
  • %VD = 6.35 ÷ 208 × 100 = 3.05%
  • Voltage at the load = 208 − 6.35 = 201.65 V

The app shows the same numbers and marks this result as above the 3% guideline. Opening the comparison shows 6 AWG at 1.96% for the same circuit.

What the model leaves out

  • Conductor reactance and power factor are not included. For AC circuits with large conductors or motor loads the real drop can be higher.
  • Three phase results assume a balanced load.
  • Copper conductors only.
  • The app does not choose a wire or breaker size, apply derating or check code compliance.

Frequently asked questions

Is the app free?

Yes. It is free to download from Google Play and shows ads. There is no paid version or subscription.

Does it work without an internet connection?

Yes. The calculations, the converter, the ampacity table and your saved calculations work offline. Ads need a network connection.

Does the app tell me which wire size to use?

No. It calculates voltage drop for the size you choose and can compare neighbouring sizes, but it does not recommend a cable. Ampacity, terminal ratings, derating, the installation method and local rules still need checking by a qualified person.

Is 3% a legal limit?

The app compares results with a common 3% voltage-drop guideline and shows it as a guideline, not as a legal limit. The limits that apply depend on the electrical code and rules where you work.

Which wire sizes and units are supported?

Copper conductors from 14 AWG to 4/0 AWG and from 1.5 to 120 mm², with lengths in feet or metres and source voltages from 1 to 2,000 V.

Which Android versions are supported?

Android 8.0 and newer.

Where are saved calculations stored?

On your phone, in the app's own storage. No account is needed. Saved calculations may be included in your Android backup.

Who makes the app?

HeloStudios. For support or privacy questions, email tugbadeveloper@gmail.com.

Get the app

Wire Size & Voltage Drop Calc is available on Google Play for Android phones.

Get it on Google Play

Reference only

This app is a reference calculator only. It is not a substitute for a licensed electrician, electrical engineer, local electrical code, or the Authority Having Jurisdiction. Incorrect wire sizing can cause fire, equipment damage, injury, or death. Always verify calculations against current local code and consult a qualified professional before installation.