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Roof Patch Material Coverage Calculator

ANA›Life Services Authority›National Calculator Authority›Roof Patch Material Coverage Calculator

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Roof Patch Material Coverage Calculator

Calculate the total roofing patch material needed for your repair project, accounting for overlap and waste.

Damaged Area Length (ft)

Damaged Area Width (ft)

Overlap on Each Side (in)

Waste Factor (%)

Roll/Sheet Width (ft)

Roll/Sheet Length (ft)

Calculate

function rooCalc() { var resEl = document.getElementById('roo-result'); var errEl = document.getElementById('roo-error'); resEl.style.display = 'none'; errEl.style.display = 'none';

// --- Read inputs --- var length = parseFloat(document.getElementById('roo-length').value); var width = parseFloat(document.getElementById('roo-width').value); var overlapIn = parseFloat(document.getElementById('roo-overlap').value); var wastePct = parseFloat(document.getElementById('roo-waste').value); var rollW = parseFloat(document.getElementById('roo-roll-width').value); var rollL = parseFloat(document.getElementById('roo-roll-length').value);

// --- Validation --- var errors = []; if (isNaN(length) || length 100) errors.push("Waste factor must be between 0 and 100."); if (isNaN(rollW) || rollW 0) { errEl.innerHTML = "Please fix the following:" + errors.map(function(e){ return ""; }).join('') + ""; errEl.style.display = 'block'; return; }

// --- Core Formulas --- // Convert overlap from inches to feet var overlapFt = overlapIn / 12;

// Patch dimensions = damaged dimension + 2 × overlap (both sides) var patchLength = length + 2 * overlapFt; // ft var patchWidth = width + 2 * overlapFt; // ft

// Net patch area (before waste) var netArea = patchLength * patchWidth; // sq ft

// Total material area needed (with waste factor) var totalArea = netArea * (1 + wastePct / 100); // sq ft

// Area per roll/sheet var rollArea = rollW * rollL; // sq ft

// Number of rolls/sheets required (ceiling) var rollsNeeded = Math.ceil(totalArea / rollArea);

// Total purchased area var purchasedArea = rollsNeeded * rollArea; // sq ft

// Leftover material var leftover = purchasedArea - totalArea; // sq ft

// Convert sq ft to squares (1 roofing square = 100 sq ft) var squaresNeeded = totalArea / 100;

// --- Display Results --- resEl.innerHTML = "### Results " + "" + "Damaged Area" + (length * width).toFixed(2) + " sq ft (" + length.toFixed(2) + " ft × " + width.toFixed(2) + " ft)" + "Patch Dimensions (with " + overlapIn.toFixed(1) + "″ overlap)" + patchLength.toFixed(2) + " ft × " + patchWidth.toFixed(2) + " ft" + "Net Patch Area" + netArea.toFixed(2) + " sq ft" + "Total Area Needed (incl. " + wastePct.toFixed(0) + "% waste)" + totalArea.toFixed(2) + " sq ft" + "Roofing Squares Needed" + squaresNeeded.toFixed(3) + " squares" + "Roll/Sheet Coverage" + rollArea.toFixed(2) + " sq ft each (" + rollW.toFixed(1) + " ft × " + rollL.toFixed(1) + " ft)" + "Rolls / Sheets to Purchase" + rollsNeeded + "" + "Total Purchased Area" + purchasedArea.toFixed(2) + " sq ft" + "Leftover Material" + leftover.toFixed(2) + " sq ft" + ""; resEl.style.display = 'block'; }

#### Formulas Used

1. Patch Dimensions

Patch Length = Damaged Length + 2 × Overlap Patch Width  = Damaged Width  + 2 × Overlap

Overlap is added to both sides (left/right and top/bottom) to ensure a watertight seal.

2. Net Patch Area

Net Area (sq ft) = Patch Length × Patch Width

3. Total Material Area (with Waste)

Total Area = Net Area × (1 + Waste Factor / 100)

4. Rolls / Sheets Required

Roll Area = Roll Width × Roll Length Rolls Needed = ⌈ Total Area ÷ Roll Area ⌉  (ceiling — always round up)

5. Roofing Squares

Squares = Total Area ÷ 100   (1 roofing square = 100 sq ft)

#### Assumptions & References

More Calculators

References

Related Authorities

Life Services Authority › Professional Services Authority › Trade Services Authority › United States Authority ›