Calculate the minimum required AWG for your electrical circuit
Copper
Aluminum
DC / AC Single Phase
AC Three Phase
Recommended AWG:–
Calculated Voltage Drop:–
Wire Area (mm²):–
Resistance (Ohms):–
How to Calculate Wire Gauge
To calculate gauge requirements accurately, you must consider the electrical resistance of the conductor material, the total length of the circuit, and the maximum allowable voltage drop for your specific application.
The Physics of Gauge: As current flows through a wire, the internal resistance of the metal causes a drop in voltage. This energy is lost as heat. If the wire is too thin (higher gauge number), the resistance is higher, leading to excessive heat and potentially dangerous conditions or equipment failure.
Key Variables in Calculation
Amperage (Current): The amount of electrical flow. Higher amperage requires a thicker wire (lower AWG).
Distance: The longer the wire, the more resistance it has. You must account for the full circuit path.
Voltage Drop: For critical electronics, a 3% drop is standard. For lighting or non-critical loads, 5-10% may be acceptable.
Material: Copper is more conductive than aluminum, meaning a copper wire can be thinner than an aluminum wire to carry the same load.
Common AWG Standards Table
AWG
Diameter (mm)
Max Amps (Copper)
4
5.189
60-85
8
3.264
40-50
10
2.588
30
12
2.053
20
14
1.628
15
function calculateWireGauge() {
var voltage = parseFloat(document.getElementById('voltage').value);
var current = parseFloat(document.getElementById('current').value);
var distance = parseFloat(document.getElementById('distance').value);
var dropPct = parseFloat(document.getElementById('allowableDrop').value);
var material = document.getElementById('material').value;
var phaseFactor = parseFloat(document.getElementById('phase').value);
if (isNaN(voltage) || isNaN(current) || isNaN(distance) || isNaN(dropPct)) {
alert("Please enter valid numerical values.");
return;
}
// Resistivity (Rho) in Ohm-cmil/ft
// Copper: 10.4, Aluminum: 17.0
var rho = (material === 'copper') ? 10.4 : 17.0;
// Allowable Voltage Drop (Actual Volts)
var vDropMax = (dropPct / 100) * voltage;
// Circular Mils Formula: CM = (Rho * I * L * Factor) / Vdrop
// L is one-way distance in feet
var circularMils = (rho * current * distance * phaseFactor) / vDropMax;
// AWG Lookup Table (Circular Mils)
var awgTable = [
{awg: "4/0", cmil: 211600},
{awg: "3/0", cmil: 167800},
{awg: "2/0", cmil: 133100},
{awg: "1/0", cmil: 105600},
{awg: "1", cmil: 83690},
{awg: "2", cmil: 66360},
{awg: "4", cmil: 41740},
{awg: "6", cmil: 26240},
{awg: "8", cmil: 16510},
{awg: "10", cmil: 10380},
{awg: "12", cmil: 6530},
{awg: "14", cmil: 4110},
{awg: "16", cmil: 2580},
{awg: "18", cmil: 1620},
{awg: "20", cmil: 1020},
{awg: "22", cmil: 640}
];
var recommendedAWG = "Smaller than 22";
var finalArea = 0;
for (var i = awgTable.length – 1; i >= 0; i–) {
if (awgTable[i].cmil >= circularMils) {
recommendedAWG = awgTable[i].awg;
finalArea = awgTable[i].cmil * 0.0005067; // convert cmil to mm2
break;
}
if (i === 0 && circularMils > awgTable[0].cmil) {
recommendedAWG = "Larger than 4/0 (Consult NEC)";
finalArea = circularMils * 0.0005067;
}
}
// Actual Voltage Drop Calculation based on chosen AWG
// Using the original target CM for the display
var actualVDrop = (rho * current * distance * phaseFactor) / circularMils;
var totalResistance = (rho * distance * phaseFactor) / circularMils;
document.getElementById('resAWG').innerText = recommendedAWG;
document.getElementById('resVDrop').innerText = actualVDrop.toFixed(2) + " V (" + dropPct.toFixed(1) + "%)";
document.getElementById('resArea').innerText = finalArea.toFixed(3) + " mm²";
document.getElementById('resResistance').innerText = totalResistance.toFixed(4) + " Ω";
document.getElementById('gaugeResultBox').style.display = 'block';
}