Drywall Calculator — HomeCalcPro

📋 Drywall Calculator

Room Length (ft)

Room Width (ft)

Ceiling Height (ft)

Drywall Sheet Size

Number of Doors

Number of Windows

Include Ceiling?

📊 Drywall Materials Needed

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Drywall Installation Tips

Use 5/8" Type X drywall for garages and fire-rated walls.
Use moisture-resistant greenboard or cement board in bathrooms and kitchens.
Standard screws: drive every 16 inches on studs and ceiling joists.
Budget about 1 lb of screws per 500 sq ft of drywall.
One 5-gallon bucket of joint compound covers approximately 200–250 sq ft.

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How to Use This Calculator

Enter the room length, width, and ceiling height in feet.
Select your drywall sheet size — 4×8 (32 sq ft) is standard; 4×12 sheets reduce seams in rooms with 9–10 ft ceilings.
Input the number of doors and windows — the calculator deducts these openings from total area automatically.
Choose whether to include the ceiling. Ceiling drywall uses the same sheet sizes but requires screwing into joists at 12-inch intervals.
The calculator outputs sheets needed (with 10% waste), joint compound buckets, tape footage, and screws by weight.

The Formula Explained

Wall Area = 2 × (L + W) × H | Net Area = Wall Area − Doors − Windows + Ceiling | Sheets = Net Area ÷ Sheet Size × 1.10

Each standard door deducts 21 sq ft (3×7) and each window deducts 15 sq ft (3×5) from gross wall area. The 10% waste factor accounts for cut pieces around outlets, irregular corners, and damaged sheets. Joint compound is estimated at one 5-gallon bucket per 225 sq ft of drywall — three coats (tape, block, finish) are standard. Plan for approximately 10 linear feet of tape per 100 sq ft of drywall surface.

Material Buying Guide

Not all drywall is the same — choosing the right type for each application prevents costly repairs later:

Standard 1/2" Drywall: Used for most interior walls and ceilings. Lightest and easiest to handle. The most common choice for residential remodels.
5/8" Type X (Fire-Rated): Required in garages, between units in multi-family buildings, and around mechanical rooms. Heavier but provides 1-hour fire separation. Don't substitute 1/2" in fire-rated applications.
Moisture-Resistant (Green Board / Purple Board): For bathroom walls outside the wet zone (not inside the shower). Not a substitute for cement backer board in direct water contact areas.
Cement Backer Board (Hardiebacker, Durock): Required behind shower tile and tub surrounds. Won't absorb water or degrade. Also used under tile on floors. NOT drywall — budget separately.
Joint Compound: All-purpose compound works for all three coats. Pre-mixed 5-gallon buckets cover 225–250 sq ft per bucket. Lightweight compound sands easier but takes longer to dry.
Drywall Screws: Use 1-1/4" coarse thread for 1/2" drywall to wood studs. Use 1-5/8" for 5/8" drywall. Budget 1 lb per 500 sq ft of drywall.

Frequently Asked Questions

How do I calculate drywall for a room with vaulted ceilings?

For vaulted ceilings, calculate the sloped area as a triangle: base × height ÷ 2, then add it to your flat ceiling area. Add 20% waste instead of 10% due to the angled cuts. Use 4×12 sheets where possible to minimize seams on long sloped runs.

How many coats of joint compound do I need?

Standard drywall finishing requires three coats: a tape coat (embedding tape over seams and corners), a block coat (filling low spots), and a finish coat (thin skim for a smooth surface). Each coat must dry fully before the next — typically 12–24 hours depending on humidity and temperature.

Can I drywall over existing plaster walls?

Yes — this is called "furring over plaster" and is common in older homes. Use 3/8" drywall to minimize added thickness. Locate studs carefully and use longer screws (2-1/2" to 3") to reach through the plaster and lath into the framing. This avoids the mess of full plaster removal.

What screw spacing should I use?

On walls: screw every 16 inches along studs, and every 8 inches at panel edges. On ceilings: every 12 inches along joists (the extra fasteners resist gravity-induced sag). Drive screws just below the surface without breaking the paper — a dimple, not a hole.

How much does drywall installation cost professionally?

Professional drywall hanging and finishing runs $1.50–$3.50 per square foot for a complete job (hang, tape, finish to Level 4). Level 5 finish (skim coat entire surface) adds $0.50–$1.00/sq ft. A 2,000 sq ft home typically costs $3,000–$7,000 for complete drywall.

🏗️ Pro Tip: Always order 10% more drywall sheets than your calculation shows — cuts and off-square walls create waste fast. For rooms with cathedral ceilings or angled walls, order 15% extra. Returning unopened boxes costs nothing; a second trip to the hardware store mid-project costs time and momentum.