Roofing Calculator
Estimate total roof area, roofing squares, shingle bundles, underlayment, ridge length and project cost for gable, hip, shed and flat roofs — with engineering drawings and a printable PDF report.
Material cost estimate (optional)
How to estimate roofing materials
Three simple steps to a complete roof area and shingle estimate.
Gable, hip, shed, flat or custom — choose the shape so the right surface geometry and ridge calculation are applied.
Add plan length, width and pitch (ratio or degrees), plus overhang and wastage allowance. Metric and imperial units both work.
Total roof area, roofing squares, shingle bundles, underlayment, ridge length and optional cost — clearly broken down.
Roofing Calculator — Free & Accurate
Our roofing calculator helps contractors, estimators, roofers, and DIY homeowners work out exactly how much material a roof will need and what it will cost. Pick a roof type — gable, hip, shed, flat, or custom — enter the plan dimensions and pitch, and get a complete material and cost estimate in seconds.
Roof surface area is computed from your plan geometry multiplied by a pitch factor that accounts for the actual sloped surface. For a roof pitch given as X:12 (rise per 12 units of run), the pitch factor is √(X² + 144) ÷ 12. For pitch given in degrees, it's 1 ÷ cos(angle). The calculator adds your overhang on all eaves before applying the pitch factor, so the result reflects the real coverage area — not just the building footprint.
Once the base roof area is known, the tool applies your wastage allowance (typically 5–15% depending on roof complexity), then converts to industry-standard roofing squares (1 square = 100 ft² of roof) and shingle bundles (~3 bundles per square for standard asphalt shingles). Underlayment is estimated in rolls (~400 ft² each), ridge length is auto-computed per roof type, and an optional cost section covers shingles, underlayment, ridge cap and labor in your local currency. Everything runs in your browser — no signup, no data sent to any server.
Why use this calculator?
Built for the site, not the spec sheet — simple, fast, and accurate.
No spreadsheets, no formulas to memorise. Type your sizes, hit calculate, and you're done.
Applies pitch-factor geometry to convert plan area into real sloped surface area, and adds overhangs and wastage automatically.
Everything runs in your browser. Your dimensions never leave your device.
Mix metres, feet, inches, and centimetres on the same job — the math converts cleanly.
Reports total roof area, roofing squares, shingle bundles and ridge length — exactly what your roofer and material supplier need to quote.
Open it on your phone right at the workshop. Fully responsive, no app needed.
Related construction tools
Free, browser-based, and built the same way as the rest of the DailyToolsAI construction suite.
Frequently asked questions
Plan area (also called footprint) is the area of the building as seen from directly above — length × width on the floor plan. Actual roof area is the real sloped surface that needs to be covered with shingles or other roofing material, which is always larger than the plan area on any pitched roof. The calculator multiplies the plan area (including overhangs) by a pitch factor derived from your roof pitch, giving you the true material area. For a flat roof the pitch factor is 1.0; for a 6:12 pitch it's about 1.118; for a 12:12 (45°) pitch it's 1.414.
Roof pitch is the steepness of the slope, expressed as rise-over-run. In US practice it's given as X:12 — the number of vertical inches of rise per 12 inches of horizontal run. A 4:12 roof rises 4 inches over every foot of horizontal travel; a 12:12 roof rises an inch for every inch. The steeper the pitch, the more roof surface you need to cover the same building footprint. The pitch factor is √(X² + 144) ÷ 12 for an X:12 ratio, or 1 ÷ cos(angle) when pitch is given in degrees. Multiply your plan area (with overhangs) by this factor to get the actual roof surface area.
Wastage covers cuts, overlaps at hips and valleys, starter and ridge courses, and the few damaged or mis-cut shingles every job produces. Typical figures: 5% for a simple gable roof with no valleys, 10% for a standard roof with normal cuts and ridge work, 15% for a more complex roof with hips, valleys and multiple pitches, and 20% for very cut-up roofs with lots of dormers and intersections. The default is 5% — bump it up when you know the layout is going to generate more offcuts. Better to order one extra bundle than make a second trip to the supplier.
For standard three-tab and architectural asphalt shingles, a roofing square (100 ft² of roof surface) takes roughly 3 bundles. The calculator divides your wastage-adjusted roof area by 100 to get squares, then multiplies by 3 and rounds up to the nearest whole bundle. Premium or specialty shingles can take 4 or even 5 bundles per square — check the bundle's coverage label and adjust accordingly. Bundles are deliberately rounded up so you finish the roof with material on hand instead of running short on the last course.
Yes. Every dimension has its own unit picker, so you can enter the length in metres, the width in feet and the overhang in inches on the same calculation. The math converts everything internally and reports the roof area in both ft² and m², so it matches whatever your supplier or roofer quotes in.