Drywall Calculator
Calculate drywall sheets, joint compound, tape, and screws needed
Calculate Drywall
Complete material list
Total wall square footage
Optional ceiling area
Typical: $10-15/sheet
10% for standard rooms
💡 Drywall Pro Tips
- 1Use 4x12 sheets for rooms with 9-10 ft ceilings to minimize seams
- 21/2" drywall for walls, 5/8" for ceilings (better sag resistance)
- 3Hang ceiling sheets first, then walls. Walls support ceiling edges
- 4Three coats of mud: tape coat, fill coat, and skim coat for smooth finish
- 5Use moisture-resistant (green board) in bathrooms and kitchens
Related Calculators
How to Use This Calculator
Begin by measuring your room dimensions to calculate the total wall and ceiling area requiring drywall. Measure the length and width of each wall, then multiply length times height to get wall area in square feet. For example, a 12-foot wall that's 8 feet tall contains 96 square feet. Calculate all four walls and sum the totals. For ceiling area, multiply room length times width. A 12×15 room has 180 square feet of ceiling. Don't subtract for doors or windows initially—drywall pros typically ignore small openings and count them as waste, simplifying calculations.
Select your drywall sheet size from the calculator options: 4×8 (32 sq ft), 4×10 (40 sq ft), or 4×12 (48 sq ft). Standard 4×8 sheets are easiest to handle and fit through most doorways, making them ideal for DIYers. However, longer sheets reduce seam count—a room with 8-foot ceilings benefits from 4×8 sheets, but 9-10 foot ceilings should use 4×10 or 4×12 sheets hung horizontally to eliminate vertical seams. Fewer seams mean less taping, faster installation, and stronger walls.
Enter the price per sheet in your local market. Standard 1/2-inch drywall costs $10-15 per 4×8 sheet at big box stores, with bulk pricing available at drywall supply yards for large projects. Moisture-resistant (green board) costs $13-17 per sheet and is required for bathrooms and laundry rooms. Fire-resistant (Type X) runs $12-16 per sheet and may be code-required for garages or shared walls. Lightweight drywall costs slightly more ($14-18) but is easier to handle. Add 10-15% waste factor to account for cuts, damaged sheets, and fitting around openings.
Review your results showing total sheets needed, screws required (28-32 screws per sheet, sold in boxes of 100-250), joint tape footage (perimeter of all sheets), and joint compound (mud) by the gallon. The calculator provides a complete material list plus estimated cost. Order 10% extra materials—running out of mud mid-project means inconsistent texture and visible patch repairs. Plan for three coats of mud: taping coat (embed tape), fill coat (build up seams and fill screw holes), and skim coat (final smooth finish). Budget 0.5-1 gallon of mud per 100 sq ft of drywall.
Understanding Drywall Calculations
Drywall thickness selection significantly impacts strength, soundproofing, fire resistance, and sag resistance. Standard 1/2-inch drywall works for most wall applications with 16-inch stud spacing. However, 5/8-inch drywall is mandatory for ceilings to prevent sagging—the extra thickness handles the weight and spanning better. Some jurisdictions require 5/8-inch Type X (fire-rated) for garages, utility rooms, or shared walls in multifamily housing. Sound-deadening drywall is 5/8 inch thick with enhanced density for noise reduction, costing $35-45 per sheet versus $10-15 for standard sheets.
Sheet orientation affects both strength and finishing workload. Hang drywall sheets horizontally (perpendicular to studs) whenever possible—this maximizes strength by spanning more studs and reduces the number of vertical seams that are prone to cracking. Horizontal hanging creates a seam at the typical 48-inch height, which is easier to tape and finish because you're working at a comfortable height rather than reaching overhead. Vertical hanging makes sense only in very tall rooms where horizontal sheets don't reach the ceiling, or in small closets where vertical sheets minimize cuts.
Taping and mudding represents 70% of the labor in a drywall project, far exceeding hanging time. Three coats minimum are required: the taping coat (apply tape over seams while wet mud), the filling/second coat (build up joints and fill fastener dimples), and the finish/skim coat (final smoothing). Allow 24 hours drying time between coats. Sanding between coats creates massive dust—use pole sanders with vacuum attachments. Many pros apply a fourth coat for critical areas like ceilings or archways. Poor taping shows through paint as ridges, shadows, or cracks.
Fastener spacing follows code requirements for structural integrity and prevents screws from popping through paint years later. Screws should be placed every 12 inches on ceilings and 16 inches on walls along each stud/joist. Edge screws go 3/8 inch from the edge, field screws sit at least 3/8 inch from any edge. Drive screws just deep enough to dimple the paper without breaking it—too deep breaks the paper and weakens holding power, too shallow leaves bumps requiring excess mud. Professionals use auto-feed screw guns that drive perfect depth every time.
Moisture resistance is critical in wet areas and dramatically affects material choice. Standard drywall in bathrooms or laundry rooms leads to mold growth, sagging, and failure. Green board (moisture-resistant drywall) contains wax additives that resist water absorption—use it on bathroom walls and ceilings not directly in shower areas. Purple board (mold-resistant) offers superior moisture and mold resistance for shower surrounds and high-moisture areas. Cement board is mandatory for tile shower surrounds as true tile backer. Never use moisture-resistant boards as a structural material behind heavy tile—they lack the strength.
Formula & Calculations
Calculate total wall area by summing all wall faces. For a rectangular room with length L, width W, and ceiling height H: Wall Area = 2(L + W) × H. A 12×15 room with 8-foot ceilings: 2(12+15) × 8 = 2(27) × 8 = 432 square feet of walls. For irregular rooms, calculate each wall individually and sum areas. Don't subtract doors or windows in preliminary calculations—material waste from cuts usually equals or exceeds these openings. Ceiling area = Length × Width. For our example: 12 × 15 = 180 square feet.
Determine sheets required by dividing total area by sheet size. For 4×8 sheets (32 sq ft each): Wall sheets needed = 432 ÷ 32 = 13.5, round UP to 14 sheets. Ceiling sheets = 180 ÷ 32 = 5.6, round to 6 sheets. Total 20 sheets for this room. Always round up—you cannot buy partial sheets. Add waste factor: 20 × 1.10 (10% waste) = 22 sheets. The waste factor accounts for damaged sheets, cutting errors, and fitting challenges around electrical boxes and fixtures. Experienced pros use 5% waste, DIYers should use 10-15%.
Calculate fasteners needed: 28-32 screws per sheet is the typical requirement (12-inch spacing on ceilings, 16-inch on walls). For 22 sheets: 22 × 28 = 616 screws. Screws sold in boxes of 100-250: 616 ÷ 100 = 6.16 boxes, purchase 7 boxes. Coarse-thread screws ($8-12 per box of 100) for wood studs, fine-thread ($9-13 per box) for metal studs. Length: 1-1/4 inch screws for 1/2-inch drywall, 1-5/8 inch for 5/8-inch drywall. Add 25% for backup—dropped screws, bad threads, and difficult areas mean you'll need extras.
Joint compound (mud) calculation: approximately 0.05 gallons per square foot of drywall for three coats. Total drywall surface (walls + ceiling): 432 + 180 = 612 sq ft. Mud needed: 612 × 0.05 = 30.6 gallons. Round to 31 gallons, or 1 gallon per 20 sq ft. Mud is sold in 1, 3.5, 4.5, and 5-gallon buckets. Buy 7 five-gallon buckets (35 gallons total) providing margin for learning curve and repairs. Taping tape: approximately 40-50 feet per sheet × 22 sheets = 880-1100 feet ÷ 250 ft per roll = 4-5 rolls. Joint tape costs $3-5 per 250-foot roll. Total cost: (22 sheets × $12) + (7 boxes screws × $10) + (7 buckets mud × $15) + (5 tape rolls × $4) = $264 + $70 + $105 + $20 = $459 for materials.
Key Factors to Consider
Ceiling height and joist spacing critically impact sheet selection and hanging difficulty. Standard 8-foot ceilings work perfectly with 4×8 sheets hung horizontally. Nine-foot ceilings pose a challenge—you can use 4×8 sheets with a 12-inch horizontal strip at the bottom (creating an extra seam), or invest in 4×10 or 4×12 sheets that span the height in one piece. Ten-foot ceilings definitely benefit from 4×10 sheets. Joist spacing also matters—16-inch centers are standard, but 24-inch centers require 5/8-inch drywall or 1/2-inch sheets hung perpendicular to joists to prevent sagging. Verify joist spacing before ordering materials.
Moisture levels in the room dictate appropriate drywall type and dramatically affect longevity. Standard white paper-faced drywall suffices for dry areas like bedrooms and living rooms. Bathrooms and laundry rooms require moisture-resistant (green board) or mold-resistant (purple board) drywall on walls and ceilings—standard drywall in moist environments grows mold within months and sags. Shower and tub surrounds require cement board or similar tile backer, not drywall of any type. Basements may benefit from mold-resistant drywall throughout. Garage walls often need Type X fire-rated drywall per building code. Using wrong drywall type voids insurance and creates health/safety hazards.
Taping and finishing technique affects final appearance more than hanging precision. Three coats minimum for all joints and screws: (1) Taping coat: 6-inch knife, embed tape fully, (2) Fill coat: 8-10 inch knife, build up joint compound, feather edges, (3) Finish coat: 12-inch knife, smooth skim coat, feather 12-18 inches beyond joint. Allow 24 hours drying between coats or longer in humid conditions. Sanding between coats is optional but recommended—light sanding knocks down ridges and bubbles. Final sanding before priming is mandatory. Poor finishing shows through any paint as ridges, shadows, and cracks.
Screw depth and spacing follow strict code requirements preventing future callbacks. Screws driven too deep break the paper face, destroying holding power—these pull through the drywall creating "pops" that appear months or years later as bumps in painted walls. Screws too shallow create bumps requiring excessive mud. Ideal depth: slight dimple in the paper without breaking it. Screw spacing: 12 inches on center maximum for ceilings (16 inches on walls), with perimeter screws 3/8 inch from edges. Many pros add extra screws (8-10 inch spacing) on ceilings as insurance against sag. Auto-feed screw guns ensure consistent depth; manual screwing requires practice.
Seam placement strategy significantly affects crack probability and finish quality. Horizontal installation (perpendicular to studs) is stronger because sheets span more supports, reducing sag and cracking. Stagger seams between adjacent rows—never align seams in a straight line across multiple sheets as these become weak points prone to cracking. Avoid placing seams over door and window headers if possible—these high-stress areas crack easily. In long hallways, one continuous sheet is better than multiple shorter sheets. Inside corners are easier to finish than outside corners—outside corners need metal corner bead ($2-3 per 8-foot piece) for protection and crisp edges. Plan your sheet layout before starting to minimize challenging seam locations.
Frequently Asked Questions
1How many sheets of drywall do I need for a 12x12 room?
A 12x12 room with 8-foot ceilings requires approximately 15-17 sheets of 4×8 drywall (including ceiling). Wall calculation: 2(12+12) × 8 = 384 sq ft ÷ 32 sq ft per sheet = 12 sheets for walls. Ceiling: 12 × 12 = 144 sq ft ÷ 32 = 4.5 sheets, round to 5 sheets. Total 17 sheets before waste factor. Add 10% waste: 17 × 1.10 = 18.7, purchase 19 sheets. Cost at $12/sheet = $228 for drywall. Add $80-100 for mud, tape, and screws. Total material cost approximately $300-330. Labor for professional installation runs $1.50-3.00 per sq ft, or $800-1600 for this room.
2What size drywall should I use?
1/2-inch drywall is standard for walls with 16-inch stud spacing. Use 5/8-inch drywall for ceilings to prevent sagging—the extra thickness handles the spanning better and reduces bounce. Some codes require 5/8-inch Type X (fire-rated) for garages or utility rooms. For sound control between rooms, use 5/8-inch on both sides of wall or specialized sound-dampening drywall. For moisture areas, use 1/2-inch or 5/8-inch moisture-resistant (green board) or mold-resistant (purple board). For tile showers, use 1/2-inch cement board, not drywall. Length selection: 4×8 for standard 8-foot ceilings, 4×10 or 4×12 for 9-10 foot ceilings or to reduce seam count.
3How much does drywall cost per sheet?
Standard 1/2-inch drywall costs $10-15 per 4×8 sheet at big box stores, with lower pricing ($8-12) available at drywall supply yards for bulk orders (50+ sheets). Moisture-resistant green board runs $13-17 per sheet. Mold-resistant purple board costs $15-20 per sheet. Type X fire-rated drywall is $12-16 per sheet. Lightweight drywall (easier handling) costs $14-18 per sheet. Larger sheets cost more: 4×10 sheets run $13-18, 4×12 sheets $16-22. Sound-dampening drywall is premium-priced at $35-45 per sheet. Prices fluctuate with material costs—bulk buying saves 15-25% versus retail.
4Can I hang drywall myself?
DIY drywall hanging is feasible with proper preparation but taping/finishing requires significant skill. Hanging requires: drywall lift ($35/day rental) for ceilings, screw gun ($50-150), T-square ($25), utility knife, and helper. Allow 2-3× professional time. Taping/finishing demands practice—expect visible seams and texture differences on first attempts. Many DIYers hang their own drywall then hire professionals for taping/finishing at $1.00-1.50 per sq ft. Full DIY on a 500 sq ft room saves $750-1500 in labor but takes 3-5 days versus 1-2 days for pros. Start with closets or garage to practice before tackling visible living spaces. YouTube tutorials help but cannot replace hands-on practice.
5How long does drywall take to install?
Professional crews hang drywall quickly: 500-750 sq ft (2-3 rooms) per day with 2-3 person crew. DIY installation takes 3-4× longer: expect 150-200 sq ft per day for beginners. Taping/mudding requires multiple days for drying: Day 1 - tape coat, Day 2 - first fill coat, Day 3 - second fill coat, Day 4 - final skim coat, Day 5 - sanding and priming. Rush jobs using quick-setting compound can compress this to 2-3 days but risk quality. A typical 12×12 room: pros complete in 2-3 days start to finish, DIYers need 5-7 days allowing proper drying. Humidity extends drying times—avoid drywall work in humid weather if possible.
6Do I need to prime drywall before painting?
Yes, drywall primer (also called PVA primer or drywall sealer) is absolutely mandatory before painting new drywall. Bare drywall and joint compound are extremely porous—without primer, you'll waste 2-3 coats of expensive paint as it soaks into the surface. Primer costs $20-30 per gallon versus $40-60 for quality paint, making it economical. Primer seals the surface, preventing uneven absorption that causes "flashing" (blotchy appearance). It also improves paint adhesion and hides color differences between gray paper face and white joint compound. Use PVA primer for new drywall, stain-blocking primer for repairs or stains. One primer coat followed by two paint coats is the professional standard. Skipping primer is the #1 mistake DIYers make.
7What tools do I need to install drywall?
Essential hanging tools: drywall screw gun ($50-150), T-square or drywall square ($25-40), utility knife with extra blades ($15), drywall saw or RotoZip ($30-90), tape measure, pencil, chalk line. Ceiling work requires drywall lift rental ($35-50/day) or two strong helpers—attempting ceiling work without a lift is dangerous and frustrating. Taping tools: 6-inch, 10-inch, and 12-inch taping knives ($8-15 each), mud pan ($8-12), pole sander with vacuum attachment ($40-80), corner tool for inside corners ($12), hawk or mud board ($15). Optional but helpful: spiral cutout tool for electrical boxes ($30-80), corner roller for tape ($8). Total tool investment: $250-400 to own, or $100-150 to rent for a weekend project plus $80-120 for taping tools you'll keep.