100 Amp Wire Size Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

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Short physics utilities are most useful when units and assumptions stay visible. 100 Amp Wire Size Calculator focuses on wire-size estimate from the fields on this page, while the notes below separate the governing relation from real-world design, measurement, and safety constraints.

What this calculator does

The 100 Amp Wire Size Calculator brings together Electrical system, Source voltage, Allowable voltage drop (V), Conductor material, One-way distance (D) around the page’s wire-size estimate. The formula section below identifies which values actually drive that result and which fields are supporting or derived quantities, so you can check the page without assuming every visible box is an independent input.

How to use it

The main fields on this page are Electrical system, Source voltage, Allowable voltage drop (V), Conductor material, One-way distance (D). Enter the quantities you actually know, keep their units consistent, and leave derived/output-style fields blank unless the formula explicitly allows solving in the opposite direction. For a clean check of wire-size estimate, change one driving quantity at a time and confirm that the result moves in the direction predicted by the equation.

How the calculation works

The legacy electrical sizing path combines a voltage-drop area with an ampacity-style area, then selects the larger. It expects phase, length, drop percent, and current-density fields; the visible 100 A page instead exposes system, distance, voltage drop in volts, and maximum temperature.

Example

For example, start with the page’s populated scenario: Electrical system = 1ph; Source voltage = 240; Conductor material = copper. Apply the equation above using the units shown on the page, then compare the calculated wire-size estimate with the displayed result. As a second check, change one physical input while holding the others fixed and confirm that the direction of change makes sense for this formula.

How to interpret the result

Interpret wire-size estimate as the output of the stated physics relation. Check units, signs, and the direction of change against the equation; when the result feeds a real design or measurement, apply the additional constraints that the page does not model.

Limitations and notes

The active legacy wire-size handler expects phase, length, drop_percent, and current_density, but this page uses system, distance, voltage_drop in volts, and max_temp. Because the fields are not aligned, do not treat the current result as code-compliant conductor sizing.