Drywall Calculator
By Taro Schenker | Updated February 11, 2026
Quick Answer: To calculate drywall, use Sheets = ceil((Wall Area - Openings) x (1 + Waste%) / Sheet Size). Deduct 21 sq ft per door and 15 sq ft per window. A standard 4x8 sheet covers 32 sq ft. Weight per 4x8 sheet: 1/4" = 38 lbs, 3/8" = 44 lbs, 1/2" = 52 lbs, 5/8" = 60 lbs. Plan for 1 gal joint compound per 480 sq ft, 1 tape roll per 500 sq ft, and 1.5 screws per sq ft. For a 12x12 room with 8' ceilings (1 door, 2 windows), you need about 12 sheets.
Calculate how many sheets of drywall you need for your walls and ceilings. Enter your room dimensions, select your sheet size and thickness, and get the exact number of sheets, plus estimates for joint compound, tape, screws, total weight, and cost.
How to Calculate Drywall
The formula for calculating drywall sheets is straightforward:
- Measure the perimeter of your room (or individual wall length).
- Multiply the perimeter by the wall height to get the total wall area in square feet.
- Subtract openings: 21 sq ft per door and 15 sq ft per window.
- Add 10% for waste from cuts, corners, and mistakes.
- Divide by the sheet area (32 sq ft for 4×8) and round up.
Drywall Sheet Coverage
Quick reference for sheet sizes, coverage area, and weight by thickness:
| Sheet Size | Area (sq ft) | Weight (1/2") | Weight (5/8") |
|---|---|---|---|
| 4' × 8' | 32 sq ft | 52 lbs | 60 lbs |
| 4' × 10' | 40 sq ft | 65 lbs | 75 lbs |
| 4' × 12' | 48 sq ft | 77 lbs | 90 lbs |
Drywall Thickness Guide
- 1/4" (6.35 mm): Used for curved walls and arches, or as a skim coat layer over existing drywall. Not structural — must be applied over a solid backing.
- 3/8" (9.5 mm): Common for repair patches and resurfacing over existing walls. Lighter and easier to handle than thicker options.
- 1/2" (12.7 mm): The standard choice for most residential walls and ceilings with 16-inch stud or joist spacing. The most widely available and affordable option.
- 5/8" (15.9 mm): Required for fire-rated walls (Type X), ceilings with 24-inch joist spacing, and soundproofing applications. Also reduces sag on ceilings.
Formula Summary
Sheet Count Formula: To calculate the number of drywall sheets, subtract openings from the gross wall area, apply the waste factor, divide by sheet size, and round up.
$$N_{\text{sheets}} = \lceil \frac{(A_{\text{gross}} - A_{\text{openings}}) \times (1 + W\%)}{A_{\text{sheet}}} \rceil$$
Room Wall Area: $$A_{\text{gross}} = 2(L + W) \times H + L \times W \text{ (if ceiling included)}$$
Openings: $$A_{\text{openings}} = N_{\text{doors}} \times 21 + N_{\text{windows}} \times 15$$
Supplies: $$\text{Joint Compound (gal)} = \lceil \frac{A_{\text{net}}}{480} \rceil$$ • $$\text{Tape (rolls)} = \lceil \frac{A_{\text{net}}}{500} \rceil$$ • $$\text{Screws} = \lceil A_{\text{net}} \times 1.5 \rceil$$
| Thickness | Weight per 4x8 Sheet (lbs) |
|---|---|
| 1/4" | 38 |
| 3/8" | 44 |
| 1/2" | 52 |
| 5/8" | 60 |
Standard Assumptions: Default waste factor is 10%. Standard door opening is 21 sq ft (3x7 ft). Standard window opening is 15 sq ft (3x5 ft). Joint compound coverage is 480 sq ft per gallon (3 coats). Tape coverage is 500 sq ft per roll. Screw density is 1.5 per sq ft. Weight is scaled proportionally for 4x10 and 4x12 sheet sizes.
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Estimates are for planning purposes only. Consult a qualified contractor for critical projects. Actual material requirements may vary based on site conditions, waste, and installation methods.
Pricing last verified: February 2026. Material prices vary by region, season, and supplier. Prices shown are national averages for planning purposes.