Thoughtful Calc

Drywall Calculator

How many sheets, rolls of tape, pails of compound, and screws you need to hang and finish a room, or several.

How do you want to measure?
For a few walls or an odd-shaped room: width × height of each wall, added up. Leave doors and windows in.
Length × width of the room. Skip it if you answered No to the ceiling.
Stud spacing, center to center (joists on a ceiling). Measure at an open wall, or find two studs with a stud finder.
Moisture- and mold-resistant board, often green or purple, is for bathrooms, laundry rooms and basements; it isn't a tile backer, so tiled tub and shower walls need cement board or another backer. Type X is the fire-rated board for a garage ceiling with a room above. The board type applies to every room here, so work out a bathroom separately from dry rooms, and a garage on its own.
Walls between the garage and the house need at least ½ in board. Some people use Type X there too.
Patio doors, a garage door opening, wide archways, and tub or shower walls that get tile backer instead. Leave ordinary doors and windows in.
Add your price (optional; we use a typical price otherwise)

Why our numbers are more realistic

Some drywall calculators use per-sheet rules of thumb for tape and compound. We use the drywall maker's own rates and the screw spacing in the installation standard. Here's what changes:

Typical calculatorThis calculatorWhy it matters
40 ft of tape per sheet About 12 ft per 4×8 sheet (370 ft per 1,000 sq ft) For a 12×14 room with ceiling, that's one 250-ft roll, not three. The 40-ft rule is about 3.4 times the maker's figure.
Half a gallon of mud per sheet 9.4 gal per 1,000 sq ft for three coats The half-gallon rule gives about 9 gallons for that room. The maker's rate gives about 5.5.
One screw count for every sheet About 28 per wall sheet and 35 per ceiling sheet (4×8) The standard calls for screws every 12 in on ceilings, not the 16 in used on walls, so ceiling sheets need about 25% more screws.

How this works

  • Sheets: wall area (perimeter × height, minus large openings) plus ceiling area, plus 10% waste for a simple room or 15% for a complex one, divided by the sheet area and rounded up. Walls and ceiling are counted separately. If you measure by wall area instead, we use your figures.
  • Doors and windows: ordinary ones aren't subtracted. Sheets run straight across them and the opening is cut out afterward, and those pieces rarely fit anywhere else. Subtract only big openings like patio doors and wide archways, under "Large openings". The paint calculator does subtract every door and window, since no paint goes on an opening, so its wall area is smaller for the same room.
  • Tape: 0.37 ft per sq ft of board, rounded up to 250- or 500-ft rolls.
  • Joint compound: 9.4 gal of ready-mix per 1,000 sq ft, enough for a tape coat and two finish coats, rounded up to whole pails of 4.5 gal.
  • Several rooms: each room's walls and ceiling are added up, then sheets are counted on the total, with walls and ceilings still counted separately.
  • Screws: sheets hung horizontally, across the framing. Every 16 in along each stud on walls and every 12 in along each joist on ceilings, plus 10% spare. With framing 24 in apart, each sheet crosses fewer studs and needs fewer screws.
  • Type X garage ceilings: the model code has ⅝ in Type X under a room hung across the joists with fasteners every 6 in, so those sheets take nearly twice the screws. Screws must reach at least ⅝ in into the wood, so use 1¼ in or longer for ⅝ in board.

Common questions

Can I figure drywall from a house's square footage?

No, measure the rooms instead. Walls usually add up to far more than the floor: a 12 × 14 room has 168 sq ft of floor but 416 sq ft of wall. If you already know the board area you're covering, choose "Wall area" and enter it.

How many sheets of drywall per bucket of mud?

About 15 sheets of 4×8 per 4.5-gal pail of ready-mix, for the usual three coats: at the maker's rate, a pail covers about 480 sq ft of board.

Can I use green board or purple board in a shower?

Not behind tile in a tub or shower. The model building code lists only tile backers there: cement board, fiber-cement board, glass-mat gypsum backer and fiber-reinforced gypsum backer. Moisture- and mold-resistant drywall isn't on the list. It's fine on the rest of the bathroom, though the code bars it where it gets direct water or constant high humidity. Codes are adopted locally, so check with your building department. Backer board isn't the whole job either: one backer maker's guide adds a waterproof membrane or vapor barrier, especially where your code requires one, so follow your backer's instructions for that layer.

How many drywall screws per sheet?

On framing 16 in apart, about 28 per 4×8 sheet on walls and 35 on ceilings. A 4×12 sheet takes about 40 on walls and 50 on ceilings. With framing 24 in apart, a 4×8 takes about 20 on walls and 25 on ceilings. The calculator adds 10% spare on top.

What this doesn't cover

  • Corner bead. Every outside corner and window return needs it: measure the total feet and buy 8 or 10 ft pieces.
  • A Level 5 finish or skim coat, which uses noticeably more compound.
  • Fire-rated assemblies other than a garage ceiling, where the approved design sets the board and screw spacing.
  • Backer board for tiled tubs and showers. Its sheet sizes and screws differ from drywall, so we don't count it.
  • Board thicknesses other than ½ in and the ⅝ in Type X option. Check the maker's spec or ask your supplier.

Sources

Related calculators

  • Paint calculator: new drywall needs a full coat of primer. Your room sizes carry over; choose "New drywall" there, or use the "Next" link in your answer, which picks it for you.

Numbers last reviewed: October 9, 2026.