Drywall Calculator

The starting point is wall area. For a rectangular room, perimeter equals 2 x (length + width), and wall area equals perimeter x wall height. A 12 x 10 ft room with 8 ft walls has a perimeter of 44 ft and a raw wall area of 44 x 8 = 352 sq ft. From that raw figure, standard openings are subtracted: a typical interior door opening removes about 21 sq ft (roughly 3 ft x 7 ft), and a typical window removes about 15 sq ft (roughly 3 ft x 5 ft), though actual rough openings vary by manufacturer and should be measured directly on larger jobs.

If the ceiling is being finished in drywall as well, its area (length x width) is added on top of the net wall area, since ceiling board is purchased and installed the same way as wall board, just oriented horizontally and usually in heavier 5/8 inch fire-rated sheets for code compliance in many jurisdictions.

A waste allowance is then applied to the net area, typically 10% to 15% for a simple rectangular room and up to 20% for rooms with many angles, soffits, or arches. The formula is Total Area = (Net Area) x (1 + Waste % / 100). This waste covers cut-offs around outlets, corners that don't align with sheet dimensions, and breakage during handling.

Sheet count is Total Area divided by the area of one sheet, rounded up, since drywall is only sold in whole sheets. A standard 4x8 sheet covers 32 sq ft, a 4x10 covers 40 sq ft, and a 4x12 covers 48 sq ft. Larger sheets reduce the number of seams (and therefore the amount of taping and mudding) but are heavier and harder to maneuver, especially on ceilings or in tight stairwells.

Ancillary materials scale with total board area rather than sheet count: joint compound is estimated at roughly 1.5 gallons per 100 sq ft for a three-coat finish, tape at about 0.4 linear feet per square foot of board (accounting for both butt joints and inside corners), and drywall screws at roughly 1.4 fasteners per square foot, which is close to the 16-inch on-center spacing pattern used on studs and joists.

Perimeter = 2 x (12 + 10) = 44 ft. Wall area = 44 x 8 = 352 sq ft. The room has one door and one window, removing 21 + 15 = 36 sq ft, leaving 316 sq ft of net wall area. The ceiling is being drywalled too, adding 12 x 10 = 120 sq ft, for a subtotal of 436 sq ft.

Applying a 10% waste factor: 436 x 1.10 = 479.6 sq ft, which this calculator rounds internally when computing sheets. Using standard 4x8 sheets (32 sq ft each), the sheet count is 479.6 / 32 = 14.99, which rounds up to 15 sheets. At $14 per sheet for standard 1/2 inch board, material for the board alone runs $210.

Joint compound: 479.6 / 100 x 1.5 = about 7.2 gallons, which is roughly 1.6 of the common 4.5-gallon buckets contractors buy, rounding up to 2 buckets at about $18 each, or $36. Tape: 479.6 x 0.4 = about 192 linear feet, well within a single 500 ft roll costing around $6. Screws: 479.6 x 1.4 = about 672 screws, weighing roughly 3.4 lbs at 200 screws per pound, or about $27 at $8 per pound of drywall screws.

Corner bead is approximated from the wall perimeter, since most rooms have a handful of outside corners; for this room that works out to roughly 7 linear feet, a single 10-foot length costing around $7. Adding it all up: $210 board + $36 compound + $6 tape + $27 screws + $7 corner bead comes to roughly $286 in materials for this one bedroom, before delivery fees, primer, or texture supplies.

Half-inch (1/2 in) standard board is the default for most residential walls and ceilings on 16-inch or 24-inch stud/joist spacing. Five-eighths inch (5/8 in) is required by many building codes for garage-to-house firewalls, some ceiling assemblies, and shared walls in multifamily construction because of its higher fire rating; it also resists sag better on ceilings with wider joist spacing.

Moisture-resistant (green or purple) board is used behind tile in bathrooms and laundry areas as a tile backer substrate in light-duty applications, though cement board or a dedicated tile backer is still preferred directly in a shower stall. Type X fire-rated board is a specific 5/8 inch product required in many fire-separation assemblies, and it typically costs 10% to 20% more than standard board.

Sheet size is a labor-versus-handling tradeoff. A 4x12 sheet on an 8 ft wall means a single sheet can run nearly the full height with one horizontal seam eliminated across a 12 ft run, cutting taping time noticeably, but it takes two people (or a panel lift) to hang safely and doesn't fit through many standard doorways without cutting. Many remodelers default to 4x8 sheets specifically because they can be carried and hung solo through existing door openings.

As of the mid-2020s, typical U.S. retail pricing runs about $11 to $16 per 4x8 sheet of standard 1/2 inch board, $14 to $20 for 5/8 inch or moisture-resistant board, and $18 to $28 for 4x12 sheets of standard board, with regional and supplier variation of 15% or more. Joint compound runs $14 to $22 per 4.5-gallon bucket, and a 500 ft roll of paper tape runs $5 to $9.

Materials are typically only 30% to 40% of a professional drywall job's total cost; labor makes up the rest. As of the mid-2020s, professional hang-and-finish labor in the U.S. commonly runs $1.50 to $3.00 per square foot of board for a standard Level 4 finish (smooth, primer-ready), with Level 5 finishes (used under glossy paint or strong raking light) adding another $0.30 to $0.60 per square foot for a skim coat over the entire surface.

For the 436 sq ft bedroom example above, professional labor at $2.00 per sq ft would run roughly $872, meaning a full turnkey job (materials plus labor) lands somewhere around $1,150 to $1,300 for that single room, not counting texture, primer, or paint. Whole-house new-construction drywall is usually quoted per square foot of finished floor area instead, commonly $1.50 to $3.50 per sq ft of house depending on ceiling height and finish level.

DIY installation saves the labor line but adds tool costs if you don't already own them: a drywall lift rental runs $40 to $60 per day and is worth it for any ceiling work, taping knives and a mud pan run $30 to $60 total, and a screw gun with a depth-sensing bit runs $40 to $80. For a single room, renting tools rarely pays for itself versus hiring a taper for just the finishing coats while hanging the board yourself.

Delivery matters more than it seems: many suppliers charge $50 to $150 to deliver and stage sheets on the correct floor, which is often cheaper than the time and vehicle wear of hauling sheets yourself, especially for anything above a single small room.

Forgetting to subtract openings, or subtracting the finished opening size instead of the rough opening, both throw off the material count. A rough opening for an interior door is typically a few inches larger in each dimension than the finished door itself, so use rough-opening dimensions from the framing plan when precision matters.

Ignoring waste on complex rooms. A simple rectangular bedroom might genuinely need only 8% to 10% waste, but a room with a bay window, a vaulted ceiling, or multiple soffits can easily need 18% to 20% because so many cuts don't use the full sheet.

Buying joint compound by weight instead of volume, or vice versa, and ending up short mid-project; compound is sold in both 4.5-gallon buckets (about 61 lbs) and smaller boxes, and mixing units when re-ordering is a common source of confusion on a job site.

Underestimating screws by assuming perimeter-only fastening; drywall needs to be screwed to every framing member it crosses, not just the edges, which is why the per-square-foot ratio (rather than a perimeter-based count) gives a more reliable estimate.

Treating corner bead as an afterthought. Outside corners left unprotected chip easily during move-in and furniture placement, and retrofitting corner bead after the walls are painted means re-texturing and repainting the whole corner run, so it is far cheaper to include it in the initial material order.