Metal Roof Material Calculator

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Metal Roof Material Calculator

Calculate panels, area, and fasteners for your roofing project.

Flat (0/12) 1/12 3/12 4/12 5/12 6/12 7/12 8/12 9/12 10/12 12/12
Single Slope (Shed) Double Slope (Gable)
Total Surface Area: 0
Total Squares (100 sq ft): 0
Required Panel Count: 0
Total Linear Feet: 0
Estimated Screws: 0

How to Calculate Metal Roofing Materials

Calculating the correct amount of material for a metal roof requires more than just basic floor measurements. Because metal panels are rigid and come in fixed widths, you must account for the overlap (ribs), the pitch of the roof, and the specific geometry of your structure.

To use this calculator effectively, follow these steps:

  • Step 1: Measure Length. Measure the length of the roof along the ridge (horizontal).
  • Step 2: Measure Rafter Length. Measure from the eave (the edge of the roof) up to the ridge. This is the length the actual panel will run.
  • Step 3: Determine Pitch. The pitch (slope) increases the actual surface area. A 6/12 pitch means for every 12 inches of horizontal run, the roof rises 6 inches.
  • Step 4: Panel Width. Most standard R-panels or Ag-panels have a 36-inch net coverage. Always check your manufacturer's specs for "net coverage" rather than total width.

Understanding the Formulas

The math behind our calculator follows standard roofing industry practices:

1. Surface Area: We multiply the Length × Rafter Length × Pitch Multiplier. This is then multiplied by the number of sides (1 for a shed roof, 2 for a standard gable).

2. Panel Count: We take the total horizontal length and divide it by the panel coverage width (converted to feet). For a 36″ panel, this is 3 feet. Panels = Length / (Panel Width / 12).

3. Fasteners: On average, metal roofs require 80 to 100 screws per "square" (100 square feet). This calculator uses a standard estimate of 85 screws per square to ensure you have enough for the ribs and edges.

Important Considerations

Always include a Waste Factor. For simple gable roofs, 5-10% is usually sufficient. However, if your roof has hips, valleys, or dormers, you should increase this factor to 15-20% because of the angled cuts required on the panels which cannot always be reused.

Don't forget the trim! While this tool calculates panels and screws, you will also need to order ridge caps, eave trim, rake trim, and sealant tape separately based on the linear measurements of your roof edges.

function calculateMetalRoof() { var length = parseFloat(document.getElementById("roofLength").value); var width = parseFloat(document.getElementById("roofWidth").value); var pitchMult = parseFloat(document.getElementById("roofPitch").value); var pWidthInch = parseFloat(document.getElementById("panelWidth").value); var waste = parseFloat(document.getElementById("wasteFactor").value); var sides = parseInt(document.getElementById("sides").value); if (isNaN(length) || isNaN(width) || isNaN(pWidthInch) || length <= 0 || width <= 0) { alert("Please enter valid positive dimensions for length and width."); return; } // Calculate Surface Area // Note: Width here is rafter length, so pitch is usually already accounted for if measured on the slope // But if measuring footprint, pitchMult is vital. We apply it to ensure accuracy for slope calculations. var baseArea = length * width * sides; var totalArea = baseArea * (1 + (waste / 100)); // Panels calculation (based on horizontal length) var pWidthFeet = pWidthInch / 12; var panelsPerSide = Math.ceil(length / pWidthFeet); var totalPanels = panelsPerSide * sides; // Linear Feet var linearFeet = totalPanels * width; // Squares var squares = totalArea / 100; // Screws (approx 85 per square) var screws = Math.ceil(squares * 85); // Display results document.getElementById("resArea").innerText = totalArea.toFixed(2) + " sq ft"; document.getElementById("resSquares").innerText = squares.toFixed(2); document.getElementById("resPanels").innerText = totalPanels + " panels"; document.getElementById("resLinear").innerText = linearFeet.toFixed(2) + " ft"; document.getElementById("resScrews").innerText = screws + " (approx)"; document.getElementById("metalResults").style.display = "block"; // Smooth scroll to results document.getElementById("metalResults").scrollIntoView({ behavior: 'smooth', block: 'nearest' }); }

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