Squares, shingle bundles, underlayment and cost for a re-roof, by footprint and pitch.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ Roofing is fall-hazard work. Use a proper roof harness and anchor, sturdy ladders and slip-resistant footwear, and stay off a wet or steep roof. If you're not confident up there, hire a pro — a fall is not worth the savings.
⚠ Most areas require a permit for a re-roof and limit you to one or two shingle layers before a full tear-off is mandatory. Check your layer count and pull the permit before you start.
⚠ In cold climates, code requires an ice-and-water shield at the eaves (typically 2 ft past the interior wall line) and often in valleys, to stop ice-dam leaks. Add it where your climate and code call for it.
| Roofing | $1,891–$2,559 |
| Fasteners & Hardware | $77–$104 |
| Total | $1,968–$2,662 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
These are affiliate links: we may earn a commission if you buy through them, at no extra cost to you. It never changes what the calculator recommends — the shopping list comes from your dimensions, not from what pays.
About this calculator
Enter your roof's footprint (the flat length and width), its pitch and the shingle type, and you get the true roof area in squares and the full material list: shingle bundles, synthetic underlayment, starter strip, drip edge, ridge cap, valley flashing, vents and nails — plus a cost estimate. It applies the slope factor for your pitch so a steeper roof correctly comes out bigger than its footprint.
Switch between a gable and a hip roof, dial in the waste for a cut-up roof with valleys, and the takeoff updates instantly. It's built for planning a re-roof — a fast, honest shopping baseline before you climb up to measure the details.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
Strip the old shingles, felt and nails down to the deck with a roofing shovel, working top-down and keeping debris off the ground and out of the gutters. Most codes only allow one or two layers before a full tear-off is required anyway.
Walk the bare deck and replace any soft, rotten or delaminated sheathing, and re-nail loose panels. Everything above only lasts if the deck under it is sound and flat.
Install drip edge at the eaves, roll out underlayment (and ice-and-water shield at the eaves and valleys where code requires), then drip edge on the rakes over the underlayment. Now the roof is dried-in.
Snap horizontal and vertical control lines so your courses run dead straight and your exposure stays consistent all the way up. Straight lines are what make a roof look professional.
Run starter strip along the eaves (and rakes for high-wind areas) with the adhesive toward the edge. It seals the first course down and stops wind from lifting the bottom edge.
Work up from the eave, staggering the joints to the pattern and nailing in the manufacturer's nail line — four to six nails per shingle depending on wind zone. Keep your courses to the chalk lines.
Weave or close-cut the valleys over valley flashing, and flash every pipe, vent and wall with the right boot or step flashing bedded in sealant. Penetrations are where roofs leak, so take your time here.
Install roof or ridge vents, then cap the ridges and hips with ridge-cap shingles running away from the prevailing wind. Finish by sweeping every square foot around the house with a magnet to collect stray nails.
Equip the job
Hand-picked categories that match the shopping list above. Links open a current selection so you can compare brands and prices.
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Keep planning
Decks & Structures
Answers
Standard three-tab and architectural shingles come three bundles to the square (100 sq ft of roof), so a bundle covers about 33 sq ft. Heavier premium and designer shingles can run four or even five bundles per square. This calculator converts your roof area into squares, then into the right number of bundles for the shingle you pick, plus waste.
DIY materials for an asphalt re-roof typically run about $150–350 per square (shingles, underlayment, drip edge, starter, ridge cap and nails), so a 20-square roof lands roughly in the low thousands in materials. Premium shingles and lots of valleys push it up. Hiring it out costs several times more because most of the price is labor. The calculator totals materials only.
A roofing square is 100 square feet of roof surface — the unit shingles and underlayment are sold and estimated by. Because a pitched roof's surface is bigger than the flat footprint underneath it, you multiply the footprint by a slope factor for the pitch to get the real area, then divide by 100 for squares.
Pitch is the rise over a 12-inch run — a roof that climbs 6 inches per foot is 6:12. The slope factor is the square root of (1 + (rise/12)²): a 6:12 roof works out to about 1.12, meaning the roof surface is 12% larger than its footprint. This calculator has the factors built in — just pick your pitch and it scales the area for you.