Roofing (Shingle) Calculator
Turn a house footprint and roof pitch into roof area, roofing squares and shingle bundles, plus starter, ridge cap and underlayment.
- Free
- No sign-up
- Formula shown
- US & metric
Your estimate
Shingle bundles (incl. 10% waste)
45 bundles
- Roofing squares
- 14.76 sq
- Actual roof area
- 1,342 sq ft
- Pitch
- 6/12 · 26.6° · factor 1.118
- Starter / ridge bundles
- 2 / 2
Show the math
- Footprint = L × W = 1,200 sq ft
- Pitch factor = √(1 + (rise ÷ 12)²) = 1.118 → roof area 1,342 sq ft
- × (1 + 10%) ÷ 100 sq ft = 14.76 squares
- × 3 bundles/square = 44.3 → 45 bundles
Shopping list & cost
| Item | Spec | Qty | Cost |
|---|---|---|---|
| Shingles (3-tab / architectural) | 3 bundles per square | 45 bundles | — |
| Starter strip | ~105 ft per bundle | 2 bundle(s) | — |
| Hip & ridge cap | ~33 ft per bundle | 2 bundle(s) | — |
| Synthetic underlayment | ~10 squares per roll | 2 roll(s) | — |
| Roofing nails | 4–6 per shingle per wrapper | ≈ 4723 | — |
Prices are what you enter under Advanced options. Estimates only — check stock and pricing with your supplier.
Quick answer A 40 × 30 ft footprint with a 6/12 pitch has about 1,342 sq ft of roof. With 10% waste that is 14.76 squares — 45 bundles at 3 bundles per square. A 12 × 9 m footprint at 6/12 needs about 43 bundles. Roof area = footprint × √(1 + (pitch ÷ 12)²).
Diagram
How to use this calculator
- Measure the house footprint including the overhangs (eaves and rakes).
- Find the pitch: rise in inches over 12 in of run. A smartphone level app works from the attic.
- Choose the roof style; hips and valleys increase waste.
- Check bundles per square on the shingle wrapper (usually 3; some heavy architectural lines are 4).
- Add eave/rake and ridge lengths under Advanced for starter and cap.
Method & assumptions
Pitch factor = √(1 + (Rise ÷ 12)²) Roof area = Footprint × Pitch factor Squares = Roof area × (1 + waste %) ÷ 100 sq ft Bundles = Squares × bundles per square, rounded up
- Square
- 100 sq ft (9.29 m²) of roof
- Rise
- inches of vertical rise per 12 in of horizontal run
Assumptions & limits
- All roof planes share one pitch; for mixed pitches calculate each section.
- Ridge/starter coverage per bundle is typical — check the product.
- Roof work is dangerous: use fall protection or hire a pro.
Rounding: purchase quantities are always rounded up to whole bags, boxes, sheets or bundles. See our methodology.
Worked examples
Imperial: 36 × 28 ft ranch, 4/12 gable
- Footprint 1,008 sq ft × 1.054 = 1,062 sq ft
- +10% = 1,169 sq ft = 11.69 squares
- × 3 = 35.1 → 36 bundles
Metric: 10 × 8 m footprint, 30° hip roof
- 30° ≈ 6.93/12 → factor 1.155
- 80 m² × 1.155 = 92.4 m²; +15% = 106.2 m² = 11.4 squares → 35 bundles
In depth: roofing shingles planning notes
Footprint, pitch and real roof area
The roof surface is larger than the footprint because it slopes. The pitch factor converts one to the other: for a pitch of rise/12, the factor is √(1 + (rise ÷ 12)²). A 4/12 roof is about 5% larger than its footprint, 6/12 about 12%, 8/12 about 20% and 12/12 about 41%. Remember to include the eaves overhang in the footprint — measure the roof outline, not the walls.
You can find the pitch by measuring the rise over 12 in of horizontal run with a level and tape in the attic, or with a pitch gauge app from a safe position. Never climb onto a steep or wet roof to measure; plans and aerial measurement services are safer alternatives.
Squares, bundles and accessories
Asphalt shingles are sold in bundles, with most three-tab and architectural shingles packaged at three bundles per square (100 sq ft). Some heavier designer shingles are four or five bundles per square, so check the wrapper. Starter strip runs along the eaves and rakes, ridge cap covers the hips and ridges, and underlayment covers the whole deck with overlaps.
Waste depends on the roof shape. A simple gable roof needs about 10% extra; a hip roof with valleys and dormers 15% or more, because every hip and valley requires angled cuts. Our calculator adds waste to the shingle count and keeps starter and ridge separate so they are not double-counted.
For metric markets, roof tiles and slates are estimated per square meter using the manufacturer's gauge and coverage, which differs by product. Roof work is hazardous; use proper fall protection or hire a qualified roofer.
Measuring complex roofs
Hip roofs, L-shaped plans and dormers are easiest to handle by splitting the footprint into rectangles, measuring each, applying the same pitch factor if all planes share a pitch and adding the results. Different pitches need separate calculations. Dormers add their own small roof area and a lot of flashing and cutting; add them separately and increase the waste for that part.
Hips and valleys do not change the total roof area for a given footprint and pitch — a hip roof and a gable roof over the same footprint at the same pitch have almost the same surface — but they add cutting waste and ridge or valley materials. That is why the waste factor, not the area, changes with roof shape.
Reference table
| Roof | Extra |
|---|---|
| Simple gable | 10% |
| Hip roof | 15% |
| Valleys, dormers, skylights | 15–20% |
Key facts
- 1 roofing square
- 100 sq ft = 9.29 m²
- Bundles per square (3-tab)
- 3 (typical)
- Pitch factors
- 4/12 = 1.054 · 6/12 = 1.118 · 8/12 = 1.202 · 12/12 = 1.414
Tips & common mistakes
- Never measure from the ground with guesswork — use plans, satellite measurements or measure at the eaves.
- Check whether the old roof must be stripped; local codes limit layers.
- Order shingles from one lot to avoid color variation.
Frequently asked questions
How many bundles of shingles do I need for 1,000 sq ft?
10 squares × 3 bundles = 30 bundles, plus 10–15% waste ≈ 33–35 bundles.
What is a roofing square?
A square is 100 sq ft of roof surface. Shingles are priced and sold per square.
How do I find my roof pitch?
Hold a level horizontally, measure 12 in along it, then measure straight up to the roof. That rise is your pitch (e.g. 6/12).
Does pitch change how many shingles I need?
Yes. Steeper roofs have more surface area for the same footprint — a 12/12 roof has 41% more area than flat.
How many bundles of ridge cap do I need?
Typically one bundle per 20–35 linear ft of ridge and hip, depending on product.
Sources
- GAF – roofing product installation instructions — checked 2026-10; verify before launch
- Owens Corning – shingle coverage and installation — checked 2026-10; verify before launch
- NRCA – National Roofing Contractors Association — checked 2026-10; verify before launch
Default values (bag yields, coverage rates, densities) are typical figures from manufacturer literature. Always check the label on the product you buy.
Related calculators
- Square Footage CalculatorFind the area of a room or yard in square feet, square meters and square yards — rectangles, triangles, circles and trapezoids.
- Drywall CalculatorCount drywall or plasterboard sheets for walls and ceilings, plus joint compound, tape and screws. 4×8, 4×12 and 1200×2400 mm.
- Paint CalculatorWork out gallons or liters of paint for a room, with doors, windows, coats, ceiling and primer — plus the tin sizes to buy.
Learn more in our guides
Cite or embed this calculator
DIYCalcLab. “Roofing (Shingle) Calculator.” Oct 18, 2026. https://diycalclab.com/roofing/shingle-calculator/
An embeddable version for blogs and contractor sites is planned.
Estimates only. Verify quantities with your supplier and local building codes. For structural, electrical or safety-critical work, consult a licensed professional. Full disclaimer.