The Formula Behind This Calculator
Wall area = 2 x (length + width) x ceiling height
Total area = wall area + ceiling area (if included) - (doors x 21 sq ft) - (windows x 15 sq ft)
Sheets = round up (total area / sheet area)
Screws = sheets x 32, tape = sheets x 12 linear ft, compound = about 1 gal per 100 sq ft
Drywall estimating starts with surface area, then gets practical. A standard door opening removes about 21 square feet and a typical double hung window about 15, and those deductions matter: a sheet and a half saved per opening adds up across a house. The supporting materials scale from the sheet count rather than the area, because screws go into sheets, tape covers the joints between sheets, and compound covers that tape. Twelve feet of tape per 4 by 8 sheet reflects the shared joints between neighboring sheets, and the screw count of 32 per sheet matches a standard 16 inch on center framing pattern with a normal field spacing.
Worked Example: A 12 by 10 Bedroom, Ceiling Included
A bedroom is 12 feet by 10 feet with 8 foot ceilings, one door and one window, and you are hanging the ceiling too with 4 by 8 sheets.
- Wall area: 2 x (12 + 10) x 8 = 352 square feet.
- Ceiling: 12 x 10 = 120 square feet, for a gross total of 472 square feet.
- Openings: subtract 21 for the door and 15 for the window, giving 436 square feet.
- Sheets: 436 / 32 = 13.6, round up to 14 sheets.
- Screws: 14 x 32 = 448 screws, about 2 pounds. Tape: 14 x 12 = 168 feet, so one 250 foot roll. Compound: 436 / 100 = about 4.4 gallons, so one 4.5 gallon pail.
- Budget: 14 sheets at $13 to $18 is $182 to $252, plus roughly $30 to $40 for the pail of compound, tape and screws. Call it $210 to $292 in October 2026 national retail pricing.
Run the same room with walls only in the calculator and the count drops to 11 sheets, which shows why the ceiling is a quarter of a typical room job. If the ceiling is staying and only the walls are being redone, that one toggle saves real money and a lot of overhead work.
A Complete Guide to Estimating Drywall for a Room
Drywall is bulky, fragile and sold by the sheet, which makes it the least forgiving material to estimate badly. Order light and you pay for a second delivery or a mid job store run with a vehicle full of everything except drywall. Order heavy and the extra sheets live in your garage for years. This guide covers the area math, the sheet size decision, and the supporting materials that turn sheets into a finished room.
Openings, Closets and Other Area Traps
The deductions in this calculator use standard sizes: 21 square feet for a 3 by 7 door and 15 square feet for a typical window. Adjust your thinking for the exceptions. A cased opening or a double door removes twice the standard area. A closet that you plan to drywall inside adds its own small walls back. Bay windows, knee walls in finished attics and sloped ceilings all break the simple perimeter formula, so measure those surfaces separately and add them as their own rectangles. Bathrooms deserve a note too: the walls around a tub or shower should be cement board or a rated moisture resistant system, not regular drywall, so subtract the tub surround from the drywall count and list it as backer board instead.
Choosing Thickness and Type
Half inch board is the residential standard for walls on 16 inch framing. Ceilings and 24 inch framing often call for 5/8 inch board, or 1/2 inch ceiling rated board, because standard half inch can sag between wide joists under insulation weight. Five eighths inch fire rated Type X is required on garage walls and ceilings shared with living space in most codes. Moisture resistant board belongs in bathrooms away from direct water, and paperless fiberglass faced board is the better pick in damp basements. Type changes the price, not the count, so the sheet total from this calculator stands, and the cost range moves up for specialty boards.
What Drywall Costs in 2026
As of October 2026, based on national home center pricing, a 4 by 8 sheet of 1/2 inch drywall runs about $13 to $18, with 5/8 and moisture resistant versions at $16 to $24. A 4.5 gallon pail of premixed all purpose compound is about $18 to $25, a 250 foot roll of paper tape about $6 to $9, and screws about $8 to $10 per 5 pound box. Delivery is the hidden line: many suppliers will stock sheets directly into the room for $50 to $100, which is often worth it for upper floors. Professional hanging and finishing, for comparison, runs roughly $2 to $3.50 per square foot of board in published surveys, which is why a bedroom that costs $250 in materials can quote at $1,200 finished.
Hanging Habits That Save Sheets
- Stage sheets in the room in hanging order, ceiling first, so you are not moving the stack twice.
- Measure and cut electrical box openings before the sheet goes up, using the box locations marked on the floor.
- Keep factory tapered edges together at joints and put cut edges at corners and ceilings, where they are easiest to hide.
- Order one extra sheet per room for damage and miscuts. A snapped sheet mid job costs more in time than the sheet costs in money.
- Photograph the walls before hanging if wiring or plumbing is inside: the photos are free insurance for every future anchor and repair.