How this roofing calculator works
Every line on a roofing order scales from the same number — squares of actual roof surface — so this calculator computes that once and fans it out, using the same engines as the single-purpose shingle and sheathing tools:
3 bundles · 320 nails · ⅒ roll per square · sheathing = area ÷ 32 ft²
Because the whole list shares one squares figure, the lines can never disagree with each other — or with the standalone calculators. At the defaults — a 40 × 30 ft footprint at 6/12 — the ticket totals ≈ $3,224; every line of it is worked in the takeoff math section below.
Every line on the roofing order, explained
A roofing ticket is six lines, each counted in its own unit. Here’s what each one is, and how the calculator counts it:
Shingle bundles
The field surface: three bundles per square with the waste factor applied. The shingle calculator runs this line standalone with its own materials guide — same engine, same answer.
Ridge cap bundles
Pre-cut caps over the ridge (and hips, when you have them): ridge length ÷ 25 lf per bundle, rounded up. The engine takes your roof’s length as the ridge line — a gable roof with the ridge running the long way.
Underlayment rolls
Synthetic underlayment covers 10 squares a roll, counted on the same waste-included squares as the shingles so the two lines land on the roof together.
Sheathing sheets
4×8 sheets (32 ft²) across the true roof area — the line to zero out on a reroof over sound decking, or to keep as a repair contingency. The roof sheathing calculator details this layer, nails included.
Drip edge sticks
The full perimeter in 10 ft sticks: both eaves at plan length, both rakes stretched by the pitch multiplier — the subtlety hand takeoffs miss. Eaves get it under the underlayment, rakes over.
Nails
Roughly 320 roofing nails per square (four per shingle) plus 48 per sheathing sheet — the calculator reports both counts so the fastener run to the store happens once.
Roofing material prices in 2026
Four editable prices drive the cost lines — bundle, sheet, roll and stick. Where the 2026 market typically sits:
| Item | Typical range |
|---|---|
| Architectural bundle | $40–50 |
| Ridge cap bundle | $45–70 |
| 7/16″ OSB sheet | $18–28 |
| Synthetic roll (10 sq) | $40–65 |
| Drip edge stick (10 ft) | $10–15 |
| Coil nails, per square | $8–12 |
Two spec notes worth a sentence each. Underlayment: synthetic has effectively replaced felt — lighter rolls, bigger coverage, walkable when wet — and the engine’s 10-squares-per-roll figure is the common synthetic size. Sheathing: 7/16 in OSB is the standard reroof deck; step up to ⅝ in where rafters run 24 in centers and the span rating says so.
How much roofing material by roof size?
Table 2 prices whole roofs through the engine at the default pitch; Table 3 holds the footprint still and moves the pitch — the multiplier is the whole difference.
| Footprint | Squares | Bundles | Sheets | Materials |
|---|---|---|---|---|
| 30 × 24 ft | 8.05 | 27 | 28 | $1,985 |
| 40 × 30 ft | 13.42 | 45 | 47 | $3,224 |
| 50 × 30 ft | 16.77 | 56 | 58 | $3,930 |
| 60 × 36 ft | 24.15 | 80 | 84 | $5,615 |
| Pitch | Squares | Bundles |
|---|---|---|
| 4/12 | 12.65 | 42 |
| 6/12 | 13.42 | 45 |
| 8/12 | 14.42 | 48 |
| 12/12 | 16.97 | 57 |
How to measure a roof for materials
One footprint measurement drives the whole list, so take it carefully and let the engine fan it out. Dimension fields take feet-inches (40, 40 ft 6 in) or metric (12 m).
- Measure the footprint including overhangs — roof edge to roof edge, both directions.
- Enter length as the ridge direction. The engine takes the long dimension as the ridge line for the cap count and runs the rakes up the short one.
- Get the pitch — a 12 in level and a tape, or the roof pitch calculator from any rise and run you can reach.
- Set waste: 10% straight gables, 15% with hips, valleys and dormers — it applies to shingles, underlayment and sheathing together.
- Reroofing over a sound deck? Zero the sheet price to drop the sheathing line, or leave a few sheets’ worth as the rot contingency.
- List the job-specific extras the count can’t know: flashing at walls and chimneys, pipe boots, ice barrier by climate — the exclusions section below is the checklist.
Worked example: the full list for a 40 × 30 ft roof at 6/12
The defaults, worked line by line — every material from one footprint, 10% waste, default prices:
shingles = 14.76 × 3 = 44.3 → 45 bundles ≈ $1,800
ridge cap = 40 ÷ 25 = 1.6 → 2 bundles ≈ $80
underlayment = 14.76 ÷ 10 → 2 rolls ≈ $130
sheathing = (1,342 × 1.10) ÷ 32 = 46.1 → 47 sheets ≈ $1,034
drip edge = 80 + 67.1 = 147 lf → 15 sticks ≈ $180
nails = 4,723 roofing + 2,256 sheathing · total ≈ $3,224
Read the drip edge line closely — it’s the one hand math gets wrong. The eaves are plan length (2 × 40 = 80 lf), but the rakes climb the slope: 2 × 30 × 1.118 = 67.1 lf, not 60. Six missing feet of metal is a Saturday trip; the multiplier belongs on every sloped line, not just the shingles.
What this roofing estimate doesn’t include
The calculator prices the count-from-area materials. The job-specific lines below get priced per piece, per foot or per hour — walk the roof and list them:
- Flashing. Step flashing at walls, counter flashing at chimneys, W-metal in open valleys — the actual waterproofing, sized on site.
- Ice and water barrier. Eaves to 24 in inside the warm wall in cold climates (IRC R905.1.2), plus valleys and penetrations.
- Pipe boots and vents. Every penetration gets a new boot; reusing old rubber is how new roofs leak.
- Starter strips. Eaves and rakes, by the linear foot.
- Tear-off and disposal. Stripping, dumpster and dump fees — commonly $1–2 per ft² of roof.
- Ventilation. Ridge vent, intake work and baffles while the deck is open.
- Labor. The majority of a roofing invoice — $4.50–8 per ft² of roof installed is the common 2026 all-in range.
- Permits and steep-slope charges. Most jurisdictions permit reroofs; crews price harness work above 8/12.
Roofing FAQ
How do I calculate roofing materials?
Everything hangs off squares: footprint × pitch multiplier gives true roof area, divide by 100 for squares, then each material has a per-square factor. The default 40 × 30 ft roof at 6/12 is 13.42 squares — 45 bundles, 2 rolls of underlayment, 47 sheets of sheathing, 15 sticks of drip edge, about $3,224 in materials.
How many squares is my roof?
Roof area ÷ 100. A 1,200 ft² footprint at 6/12 is 1,342 ft² of actual surface — 13.42 squares. Steepness matters more than people expect: the same footprint at 12/12 is 17 squares.
How much roofing material do I need per square?
3 bundles of shingles, about 320 nails, one-tenth of an underlayment roll, and a bit over 3 sheets of sheathing if you are re-decking. The calculator applies the waste factor to all of them at once, which is where hand math usually slips.
How much drip edge do I need?
The full perimeter: both eaves plus all four rakes — and the rakes run the slope, so they get the pitch multiplier too. The default roof needs 147 lf, which is 15 ten-foot sticks. Eaves get drip edge under the underlayment; rakes over it.
How many bundles of ridge cap do I need?
Ridge length ÷ 25 lf per cap bundle, rounded up: the default 40 ft ridge takes 2 bundles. Add every hip line on a hip roof to the ridge figure — caps cover hips and ridges alike, and some premium caps run 20 lf a bundle, so check the wrapper.
Do I need new sheathing when I reroof?
Only where the deck is bad: soft spots, delamination, rot at eaves and valleys. Most reroofs replace a handful of sheets, not the field — walk the deck after tear-off and keep a contingency. Re-decking entirely is a code or insurance event, not a default.
What is in a complete roof materials list?
Shingles, ridge cap, underlayment, drip edge, nails, and sheathing if the deck is being replaced — that is this calculator. Priced separately because they are job-specific: ice-and-water barrier in cold climates, pipe boots, and any flashing at walls, chimneys and valleys.
How much does it cost to roof a house?
The default roof is about $3,224 in materials. Installed, architectural shingle roofs typically run $4.50–8 per square foot of roof area in 2026 — tear-off, steepness and access move the labor side far more than the shingle brand does.
Sources and standards
The factors in this calculator’s list come from code requirements and published product coverage:
- IRC R905.2: asphalt shingle application — slope limits, underlayment, fastening.
- IRC R905.1.2: the ice-barrier requirement the exclusions list flags for cold climates.
- Manufacturer coverage specs: 3 bundles and ~320 nails per square, 10-square rolls, 25 lf cap bundles — wrapper figures; the wrapper governs when your product differs.
- Engine parity: this page shares constants with the shingle and sheathing calculators, so the combined list can never disagree with the standalone tools.
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