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Roofing Calculator
Squares, shingle bundles, underlayment, starter, and cap from your footprint and pitch — with the math shown, not hidden.
Field measurements
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Printed from build-your-house.com/calculators/roofing — estimate only.
Methodology
How this takeoff is figured
SHEET TO-04
Roof area. Plan area is the footprint plus overhang on all four sides: (length + 2 × overhang) × (width + 2 × overhang). That flat area is then multiplied by the pitch factor √(1 + (rise/12)²) to become sloped surface — 4/12 → 1.054, 6/12 → 1.118, 8/12 → 1.202, 12/12 → 1.414.
Waste. A simple gable gets 10%, hips and valleys 15%, and a cut-up roof 20% — every hip, valley, and dormer is a cut line that throws away shingle ends. Shingles and nails are figured on the waste-added area; underlayment gets its own 10% for laps instead.
Shingles and underlayment. Architectural shingles at 3 bundles per square, rounded up to whole bundles. Synthetic underlayment comes in 10-square rolls, sized to the roof area plus 10% for laps.
Starter, cap, and drip edge. Starter strip runs the eaves and rakes — approximated with the plan perimeter, at 105 lf per bundle, with 5% added on hip roofs where every edge is an eave. Ridge and hip cap covers ~33 lf per bundle: a gable needs cap roughly the house length, hips multiply that by 1.6, and a cut-up roof by 2.1. Drip edge is the full perimeter plus 5% laps, in 10-ft aluminum sticks.
Nails. 2.5 lb of 1¼" coil roofing nails per square — about 320 nails.
L-shaped houses. The math assumes a rectangle. For an L or T, run each wing through the calculator separately and add the takeoffs — the ridge and valley lines will differ, which is also why the waste setting matters more on those roofs.
Assumptions
Coverage, waste, and pricing
ADJUST ABOVE
- Pitch factor√(1 + (rise/12)²)
- WasteGable 10% · hips 15% · cut-up 20%
- Shingle coverage3 bundles per square
- Underlayment roll10 squares, +10% laps
- Starter strip105 lf per bundle
- Ridge & hip cap~33 lf per bundle
- Coil nails2.5 lb per square
- Shingle bundle$34–$48, Aug 2026
Questions
Owner-builders ask
FAQ
How many squares is a 2,000 sq ft house roof?
It depends on the footprint, not the living area. A 40 × 30 ft single-story at 6/12 pitch with 1-ft overhangs works out to a 42 × 32 plan (1,344 sq ft), times a 1.118 pitch factor, plus 10% gable waste — about 16.6 squares to order. A 2,000 sq ft single-story (50 × 40 footprint) at the same settings runs about 26.9 squares, but a 2,000 sq ft two-story has roughly a 1,000 sq ft footprint, so two stories roughly halve the roof.
How many bundles of shingles per square?
Three. Architectural shingles are packaged so three bundles cover one square (100 sq ft of roof), and that is what this calculator uses, rounded up to whole bundles on the waste-added area — so a 16.6-square order comes to 50 bundles. Some heavyweight and specialty shingles run four or five bundles per square; check the wrapper before you order.
What does roof pitch do to material quantities?
Flat plan area gets multiplied by √(1 + (rise/12)²) to become sloped surface. At 4/12 the factor is 1.054 — barely more than flat. At 6/12 it is 1.118, at 8/12 it is 1.202, and at 12/12 it reaches 1.414 — the same footprint needs about 34% more shingles at 12/12 than at 4/12. Pitch hits labor even harder: above about 7/12, most crews charge steep-roof rates.
How much waste should I add for a hip roof?
15% — this calculator uses 15% for hips against 10% for a simple gable. Every hip is a long diagonal cut line where shingle ends get trimmed off and thrown away, and hips also consume more cap: the math here figures roughly 1.6× the house length in ridge-and-hip cap for a hip roof versus a single gable ridge. For a cut-up roof with multiple hips, valleys, and dormers, use the 20% setting.
What's not in this estimate?
Ice & water shield — required by code at eaves and valleys in cold climates, with one roll covering about 65 lf of eave — plus flashing, pipe boots, vents, labor, and tear-off disposal. Those depend on your climate, your code, and what is on the roof now, so price them from your plans and a roof-top look, not a footprint.