Check voltage drop for single, split and three phase circuits before choosing a wire size. Enter the load current, the one-way length in feet or metres, a copper conductor in AWG or mm² and the source voltage to see the drop in volts and percent and the voltage left at the load.

Wire Size & Voltage Drop Calc combines a three phase voltage drop calculator, an AWG to mm² converter and a copper ampacity reference. The calculators work offline, and each result shows its formula and the source of the values it uses.

Three phase voltage drop calculator
Choose single phase, split phase or balanced three phase. One tap sets common combinations such as 120 V single phase, 240 V split phase, 208 V or 480 V three phase, 230 V single phase and 400 V three phase, and you can still type any voltage from 1 to 2,000 V. A note appears when the drop is above the common 3% guideline. This is a resistance-based reference calculation: conductor reactance and power factor are not included, and the app does not pick a cable for you.

Compare wire sizes
Open the comparison under a voltage drop result to see the same circuit with neighbouring copper sizes: one thinner and two thicker where available. Each size shows its drop in percent on one shared scale with the 3% guideline marked. It compares voltage drop only; it is not a cable recommendation, and ampacity, terminals and other installation rules still need checking.

AWG and metric cable sizes
Use copper sizes from 14 AWG to 4/0 AWG, with resistance values from NEC Chapter 9 Table 8, or metric sizes from 1.5 to 120 mm², with resistance values from IEC 60228 corrected to the same 75 °C basis. Switching between feet and metres converts your length and shows both values.

AWG to mm² converter
Convert a supported AWG size to its cross-sectional area in mm² and its nominal diameter, or enter an area to find the smallest listed AWG size with at least that area. Unsupported sizes and impossible values get a clear message instead of a misleading number.

Copper ampacity reference
Compare the 60, 75 and 90 °C columns of NEC Table 310.16 for copper conductors from 14 AWG to 4/0, with notes on the table conditions, small-conductor overcurrent limits and termination ratings. Derating and other code conditions are not applied.

Save, reopen and share
Name and save voltage drop and conversion results on your phone, then reopen, edit, rename or delete them later. No account is needed. Copy or share voltage drop and conversion results as text; the reference-only note is always included. The app remembers your units, last phase and voltage, and offers a light or dark appearance.

Advertising needs a network connection; the calculators work without one.

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

Built by HeloStudios.