For gutter contractors and suppliers, accurately estimating the linear footage available in a specific coil is essential for inventory management and job planning. Gutter coils are typically sold by weight (pounds), but installation jobs are measured in length (linear feet). This calculator bridges that gap by determining the yield of a coil based on its material properties and dimensions.
Key Factors in Coil Calculation
To convert weight to length, three primary variables are required:
Material Density: Different metals have different densities. Aluminum is lightweight (approx. 0.0975 lbs/in³), while Copper is significantly heavier (approx. 0.321 lbs/in³).
Width: This corresponds to the size of the gutter machine. A standard 5-inch K-style gutter typically uses an 11.75-inch or 11.875-inch wide coil. A 6-inch gutter typically uses a 15-inch wide coil.
Gauge (Thickness): The thickness of the metal sheet. Common aluminum gutter gauges are 0.027″ (standard residential) and 0.032″ (heavy duty or commercial).
Formulas Used
The calculation relies on determining the volume of metal in one linear foot and multiplying it by the material density.
1. Calculate Weight per Foot: Weight/Ft = Width (in) × Gauge (in) × 12 (in/ft) × Material Density (lbs/in³)
2. Calculate Total Length: Total Length = Total Coil Weight / Weight per Foot
Common Coil Configurations
5″ Gutter (Aluminum): 11.75″ Width, 0.027″ Gauge. Yields approximately 2.7 to 3.0 feet per pound.
6″ Gutter (Aluminum): 15″ Width, 0.032″ Gauge. Yields approximately 1.8 to 2.0 feet per pound.
Copper Gutters: Due to copper's high density, the footage yield per pound is significantly lower than aluminum, often around 0.7 to 0.8 feet per pound for 16oz copper (approx 0.0216″ thick).
Why Accurate Estimation Matters
Knowing the exact footage remaining on a partial coil prevents "shorting" a job run, which results in material waste and lost time. By weighing a partial coil and running the numbers, a contractor knows exactly if they have enough material to complete a continuous gutter run without seams.
function updateDensityNote() {
var material = document.getElementById('materialType').value;
var display = document.getElementById('densityDisplay');
if (material === 'aluminum') {
display.innerText = "Density: ~0.0975 lbs/in³";
} else if (material === 'copper') {
display.innerText = "Density: ~0.321 lbs/in³";
} else if (material === 'steel') {
display.innerText = "Density: ~0.283 lbs/in³";
}
}
function calculateGutterCoil() {
// 1. Get Input Values
var material = document.getElementById('materialType').value;
var width = parseFloat(document.getElementById('coilWidth').value);
var gauge = parseFloat(document.getElementById('coilGauge').value);
var weight = parseFloat(document.getElementById('coilWeight').value);
var price = parseFloat(document.getElementById('pricePerLb').value);
// 2. Validate Inputs
if (isNaN(width) || width <= 0) {
alert("Please enter a valid coil width (e.g., 11.75 or 15).");
return;
}
if (isNaN(gauge) || gauge <= 0) {
alert("Please enter a valid gauge thickness (e.g., 0.027).");
return;
}
if (isNaN(weight) || weight 0;
if (hasPrice) {
totalCost = weight * price;
costPerFoot = totalCost / totalFeet;
}
// 8. Display Results
document.getElementById('resLength').innerText = totalFeet.toFixed(1) + " ft";
document.getElementById('resWeightPerFoot').innerText = weightPerFoot.toFixed(3) + " lbs/ft";
document.getElementById('resYield').innerText = yieldFactor.toFixed(2) + " ft/lb";
if (hasPrice) {
document.getElementById('resTotalCost').innerText = "$" + totalCost.toFixed(2);
document.getElementById('resCostPerFoot').innerText = "$" + costPerFoot.toFixed(2);
} else {
document.getElementById('resTotalCost').innerText = "N/A";
document.getElementById('resCostPerFoot').innerText = "N/A";
}
document.getElementById('resultBox').style.display = 'block';
}