🪵 Roof Sheathing Calculator — Plywood & OSB Sheets
Estimate plywood, OSB, or sheathing sheets for your roof deck
Enter total roof area, sheet dimensions, thickness, and waste buffer to get sheet count and weight estimates.
Smart Roofing Calculator — Roof Sheathing Calculator — Plywood & OSB Sheets — smartroofingcalculator.com/plywood/ — printed
After applying pitch factor
1/2" typical; 5/8" for heavy snow/wind
5–15% typical
🛒 Materials for this job
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Calculate above and your quantities fill in here.
💡 Always round up and include 10–15% extra for waste.
🛠️ How This Calculator Works
Enter your total sloped roof area. The calculator divides by sheet area, adds waste, and rounds up to whole sheets.
📐 Formula
Sheets = ⌈(Roof Area × (1 + Waste%)) ÷ (Sheet Length × Sheet Width)⌉📝 Example Calculation
For a 1,500 sq ft roof with 10% waste: • Sheets needed: ⌈1,650 ÷ 32⌉ = 52 sheets • Weight (1/2"): ~2,496 lbs
💡 Pro Tips from Roofers
- Stagger joints by 4+ feet between rows.
- Leave 1/8-inch gaps for thermal expansion.
- Use H-clips between rafters if spacing exceeds 16" OC.
- Never install wet plywood.
❓ Frequently Asked Questions
How many sheets of plywood do I need for a roof?
Divide your total roof area by 32 sq ft (4×8 sheets) and add 10-15% for waste.
What thickness plywood for a roof?
Most residential roofs use 1/2-inch CDX plywood. In heavy snow zones, 5/8-inch may be required.
Plywood vs OSB for roof sheathing?
Plywood handles moisture better; OSB is 15-20% cheaper. Both meet code for most applications.
How much is a sheet of plywood for a roof?
CDX plywood costs $25-$45 per 4×8 sheet. OSB is $18-$30 per sheet.
How do I calculate roof sheathing?
Measure the roof outline including overhangs, multiply by the pitch factor to get the sloped area, add 10% waste (15% for a hip roof), then divide by 32 sq ft per 4 x 8 sheet and round up.
Is an OSB calculator different from a plywood calculator?
No. A 4 x 8 sheet of OSB and a 4 x 8 sheet of plywood both cover 32 square feet, so the sheet count is identical. Only the price, weight and moisture behaviour differ.
How many sheets of OSB do I need for 1,000 square feet of roof?
35 sheets at 10% waste, or 36 at 15% for a hip roof. That is 1,000 sq ft of roof surface, not footprint.
What does 24/16 on a sheet of OSB mean?
It is the span rating: the panel is rated for roof framing up to 24 inches on centre and floor framing up to 16 inches on centre.
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Worked examples updated . Every figure below is computed with the same formulas as the calculator.
Roof sheathing worked example
Worked example: A 40 x 28 ft house, 12-inch overhang, 6/12 gable, 1/2-inch sheathing
- Measure to the outside of the overhang: 42 x 30 ft = 1,260 sq ft of footprint.
- Multiply by the 6/12 pitch factor, 1.1180: 1,409 sq ft of deck.
- Add 10% for cut-offs at the rakes and ridge: 1,550 sq ft.
- Divide by 32 sq ft per 4 x 8 sheet and round up: 49 sheets.
- At roughly 40 lb per 1/2-inch sheet, that is about 1,960 lb on the deck — plan a boom delivery rather than carrying it up.
49 sheets of 1/2-inch plywood or 7/16-inch OSB. The count is the same for either material; only the price and weight change.
Worked example: A hip roof: 50 x 36 ft outline at 7/12
- 1,800 sq ft x 1.1577 = 2,084 sq ft of deck.
- Hips cut every sheet at the corners, so allow 15%: 2,396 sq ft.
- 2,396 ÷ 32 = 75 sheets.
75 sheets. The hip triangles use offcuts from one side on the other, which is why 15% rather than 20% is usually enough.
Sheathing sheets by roof area
| Roof area | Sheets at 10% waste | Sheets at 15% waste | Weight, 1/2 in (approx.) |
|---|---|---|---|
| 1,000 sq ft | 35 | 36 | 1,400 lb |
| 1,500 sq ft | 52 | 54 | 2,080 lb |
| 2,000 sq ft | 69 | 72 | 2,760 lb |
| 2,500 sq ft | 86 | 90 | 3,440 lb |
| 3,000 sq ft | 104 | 108 | 4,160 lb |
These are roof areas, not house sizes. If you only have the footprint, run it through the roof area calculator or multiply by the factor in the roof pitch chart first. How many sheets come in a lift or bunk is on the OSB bundle page.
Which thickness: reading the span rating stamp
Every structural panel carries a two-number span rating such as 24/16. The first number is the maximum rafter or truss spacing in inches when the panel is used as roof sheathing; the second is for floors. Thickness alone does not tell you the rating — read the stamp.
| Panel | Typical span rating | Common use |
|---|---|---|
| 7/16 in OSB | 24/16 | Trusses at 24 in on centre, asphalt shingles |
| 15/32 or 1/2 in plywood | 32/16 | Rafters at 16 or 24 in, most re-roofs |
| 19/32 or 5/8 in plywood or OSB | 40/20 | Tile, heavy snow, or where a stiffer deck is wanted |
| 23/32 or 3/4 in | 48/24 | Long spans, heavy loads, low-slope decks with foot traffic |
At 24-inch spacing, panel clips (H-clips) between rafters support the long edges; many codes and manufacturers call for them there. Check your local code and the shingle manufacturer's minimum deck thickness before you buy — see also OSB vs plywood for a roof.
Framing walls under the roof? The stud calculator counts studs and plates for each wall.
Sheeting the inside walls too? The drywall calculator counts 4 × 8 or 4 × 12 sheets for walls and ceilings, plus mud, tape and screws.
Not sure which panel to buy? The roof sheathing thickness calculator gives the minimum span rating for your rafter spacing from IRC Table R503.2.1.1(1).
Sheathing a mansard? The mansard roof calculator gives the area of the steep lower slopes and the top, ready for a sheet count.
Framing the hips before the sheathing goes on? The hip rafter calculator gives hip and jack rafter lengths and side cuts.
Does the underlayment replace the deck? No; underlayment vs plywood explains the two layers.
Plywood, OSB, or sheathing — what's the difference?
This calculator works for all three. CDX plywood, OSB (oriented strand board), and generic roof sheathing all come in 4×8 sheets covering 32 sq ft each. The math is identical — only the price and weight differ. Use 1/2" or 5/8" CDX or OSB for most residential roofs.
How many sheets of plywood are in a bundle?
A standard bundle (also called a "lift") of 1/2" CDX plywood contains 48–56 sheets, depending on mill and sheet thickness. Common counts:
| Plywood Thickness | Sheets per Bundle | Bundle Weight (approx.) |
|---|---|---|
| 1/4" | 80 sheets | 1,800 lbs |
| 3/8" | 60 sheets | 1,950 lbs |
| 1/2" | 48 sheets | 2,300 lbs |
| 5/8" | 40 sheets | 2,400 lbs |
| 3/4" | 32 sheets | 2,400 lbs |
| OSB 7/16" | 60 sheets | 2,400 lbs |
Counts vary by manufacturer. Always confirm with your supplier before ordering full bundles.
OSB Calculator — Same Math, Different Material
To use this as an OSB calculator or OSB board calculator, just enter your roof area above. OSB sheets are also 4×8 (32 sq ft) and ship in lifts of about 60 sheets at 7/16" thickness. Most building codes accept OSB and CDX plywood interchangeably for roof sheathing.
How Many Sheets of Plywood for a 1,000 / 2,000 / 3,000 sq ft Roof?
Quick reference using 4×8 sheets (32 sq ft each) with 12% waste applied:
| Roof Area | Sheets Needed | CDX 1/2" Cost ($35/ea) | OSB 7/16" Cost ($22/ea) |
|---|---|---|---|
| 1,000 sq ft | 35 | $1,225 | $770 |
| 1,500 sq ft | 53 | $1,855 | $1,166 |
| 2,000 sq ft | 70 | $2,450 | $1,540 |
| 2,500 sq ft | 88 | $3,080 | $1,936 |
| 3,000 sq ft | 105 | $3,675 | $2,310 |
What Thickness Plywood or OSB for Roof Sheathing?
1/2" CDX plywood or 7/16" OSB meets IRC code for rafters spaced 24" on-center in most regions. In heavy snow zones (40+ psf ground snow load) or with 24" truss spacing under tile, step up to 5/8" plywood or 19/32" OSB. For 16" OC framing, 3/8" sheathing is technically allowed but rarely used. Always check your local building amendments before ordering.
Not sure which to choose? Read our deep-dive on OSB vs plywood for roof sheathing. After your deck is on, size fasteners with the roofing nails calculator and pick the right roll count with the underlayment calculator.
🔗 Related Roofing Calculators
- OSB vs Plywood for Roof — Full Comparison
- Roof Pitch Calculator — Get the pitch factor before sizing sheets
- Underlayment Calculator — Felt, synthetic & ice & water shield rolls
- Roofing Nails Calculator — Nail count for sheathing + shingles
- Hip Roof Calculator — Sheet count for four-sided hip roofs
- Rafter Length Calculator — Framing under your sheathing
- Rafter Span Chart — Max spans by lumber size & spacing
- TPO & Flat Roof Cost Calculator — Deck, insulation & membrane pricing
- Metal Roofing Cost Calculator — Installed cost over the same deck
🪜 Building a Deck With the Same Plywood?
Plywood and OSB are also used for deck substrates, sheathing, and box stairs. If you're working on a deck project alongside the roof, our sister site has dedicated calculators for deck boards, joist spacing, beam sizing, fasteners, and total cost: Smart Decking Calculator →
· Reviewed by the Smart Roofing Calculator editorial team