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Drywall · US units

Drywall Calculator — 4×8 Sheets and Cost

USG J371 is blunt: 10 sheets of 4×8 = 320 square feet, so one sheet is 32. Installation guides say divide the measured area by 32. There is no manufacturer waste percent.

Basket 2026-08-27

Room

ft
ft
ft

20 sq ft each — same Behr opening sizes used for paint. USG does not publish opening sizes.

15 sq ft each. Do not subtract electrical boxes.

Waste factor

USG J371 has no waste percent — divide net area by 32 and round up. 10% is a calculator convention.

$

USG UltraLight 4×8 1/2 in: $15.58 on 2026-08-27. Same day also showed $16.68 (zip variance). Grip-Rite 3 in screws are a shelf SKU — USG spec for 1/2 in is 1-1/4 in Type W.

Sheets to buy

17 sheets

16.947 exact · 493 sq ft net · 4×8 = 32 sq ft

$264.86

Gross walls
384 sq ft
Ceiling
144 sq ft
Doors + windows
−35 sq ft
After 10% convention
542.3 sq ft

10 sheets = 320 sq ft (USG J371). Offcuts from doors rarely become a full extra sheet, which is why the convention exists.

What calculator.net does not show

USG tells you to subtract openings large enough to matter — doors and windows — and not to nickel-and-dime electrical boxes. The 20 / 15 sq ft opening sizes here are the same Behr how-to figures used on the paint tool so a 12×12 room is comparable across calculators; USG does not publish those opening areas. 10% extra is a hangers’ convention for offcuts and broken corners, not J371.

Home Depot online listed USG Sheetrock UltraLight 1/2 in 4×8 at $15.58 on 2026-08-27. The same day also showed $16.68 depending on zip. The calculator defaults to $15.58; both numbers are on the prices page. Grip-Rite 3 in drywall screws ($5.97/lb) are in the basket as a shelf SKU only. USG’s specified fastener for 1/2 in single-layer panels is 1-1/4 in Type W, not 3 in.

Worked US example: 12×12 room, 8 ft walls, ceiling on

Gross walls = 2 × (12 + 12) × 8 = 384 sq ft
Ceiling     = 12 × 12 = 144 sq ft
Openings    = 20 + 15 = 35 sq ft
Net         = 384 + 144 − 35 = 493 sq ft
Sheets      = 493 ÷ 32 = 15.406 → buy 16 sheets
10% conv.   = 493 × 1.10 = 542.3 sq ft → 16.947 → buy 17 sheets
Cost @ $15.58 = 16 × $15.58 = $249.28   or   17 × $15.58 = $264.86
Alt zip $16.68 = 16 × $16.68 = $266.88

Citations

  1. USG. Sheetrock Brand gypsum panels submittal J371. Accessed 2026-08-27. https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/sheetrock-brand-gypsum-panels-submittal-J371.pdf — 4 × 8 ft panels: 10 sheets = 320 sq ft, so one sheet is 32 sq ft. USG installation math divides area by panel square footage. No manufacturer waste percentage. Subtract doors and windows; do not subtract electrical boxes.
  2. USG / Home Depot PDF. USG Sheetrock Brand gypsum panels installation guide. Accessed 2026-08-27. https://images.thdstatic.com/catalog/pdfImages/9f/9fe15ca9-324e-4407-b4ef-9bdbc1946a6c.pdf — 4 ft × 8 ft = 32 sq ft; 4 × 10 = 40; 4 × 12 = 48. Divide measured area by panel area. No waste factor listed.
  3. USG. Type W screws for 1/2 in gypsum panels. Accessed 2026-08-27. https://www.usg.com/content/usgcom/en/products/walls/drywall.html — USG specifies 1-1/4 in Type W screws for 1/2 in single-layer panels — not 3 in coarse-thread drywall screws. The Grip-Rite 3 in 1 lb box in the price index is a shelf SKU, not the specified fastener.
  4. Behr. How Much Interior Paint to Buy for your Home. Accessed 2026-08-27. https://www.behr.com/consumer/how-to/interior/determine-how-much-interior-paint-to-buy — Average window about 15 sq ft; average door about 20 sq ft. How-to copy discusses one coat coverage; Behr system recommendation is two coats for most color changes and new work.

These calculators estimate material takeoff for planning. They are not engineering, structural, or code advice. Confirm spans, mixes, fastener schedules, and permits with a licensed professional and the manufacturer’s current data sheet. Local shelf prices and tax are not this index.