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Drywall Calculator

Estimates the number of gypsum board sheets for walls (and optionally the ceiling) of a room with a waste allowance, plus screws at about one per square foot and joint compound at the USG rate of 10 gallons per 1,000 ft² of board.

Unit system (optional)Unit system of the length inputs (metric: m / cm / mm; imperial: ft / in). Outputs are reported in both systems. Room length (m or ft) (optional)Room length (m or ft); used with room_width and wall_height when wall_area is not given, and for the ceiling. Room width (m or ft) (optional)Room width (m or ft). Wall height (m or ft) (optional)Wall height (m or ft). Wall area (m² or ft²) (optional)Total wall area to board (m² or ft²); replaces 2 × (length + width) × height when given. Include ceiling (optional)Add the ceiling area (room_length × room_width). Openings to subtract (m² or ft²) (optional)Area of large openings (doors, windows) to deduct; small openings are usually not deducted because the cut-outs are waste. Sheet size (optional)Board size. Default 1200 × 2400 mm (metric) or 4 × 8 ft (imperial). Waste allowance (%) (optional)Extra material for cuts, breakage and offcuts, applied as a multiplier (1 + waste_percent/100). 10 % is typical for rooms with few openings; use 15 % for complex rooms.

When to use

You need to order plasterboard/drywall sheets, screws and joint compound for a room or a known wall area.

Do not use when: You need paint or wallpaper quantities for the finished wall (use paint or wallpaper), or metal-stud framing take-offs.

Formula

area = 2 × (room_length + room_width) × wall_height (or wall_area) + room_length × room_width (if include_ceiling) − openings_area; sheets = ceil(area × (1 + waste/100) / sheet_area); screws ≈ area_ft² × 1; compound_gal = area_ft² / 100; pails = ceil(compound_gal / 4.5).

Fastener spacing follows IRC R702.3.5 (screws at 16 in on walls and 12 in on ceilings with 16 in framing), which works out to roughly one screw per square foot. Compound coverage is USG's figure for taping and three-coat finishing of the joints.

Inputs

Parameter	Type	Unit	Required	Description
`unit_system`	enum: metric \| imperial		default metric	Unit system of the length inputs (metric: m / cm / mm; imperial: ft / in). Outputs are reported in both systems.
`room_length`	number	m or ft	no	Room length (m or ft); used with room_width and wall_height when wall_area is not given, and for the ceiling. Range: > 0, ≤ 1000
`room_width`	number	m or ft	no	Room width (m or ft). Range: > 0, ≤ 1000
`wall_height`	number	m or ft	no	Wall height (m or ft). Range: > 0, ≤ 100
`wall_area`	number	m² or ft²	no	Total wall area to board (m² or ft²); replaces 2 × (length + width) × height when given. Range: > 0
`include_ceiling`	boolean		default false	Add the ceiling area (room_length × room_width).
`openings_area`	number	m² or ft²	default 0	Area of large openings (doors, windows) to deduct; small openings are usually not deducted because the cut-outs are waste. Range: ≥ 0
`sheet_size`	enum: 4x8_ft \| 4x12_ft \| 1200x2400_mm \| 1200x3000_mm		no	Board size. Default 1200 × 2400 mm (metric) or 4 × 8 ft (imperial).
`waste_percent`	number	%	default 10	Extra material for cuts, breakage and offcuts, applied as a multiplier (1 + waste_percent/100). 10 % is typical for rooms with few openings; use 15 % for complex rooms. Range: ≥ 0, ≤ 50

Outputs

Output	Type	Unit	Description
`area_m2`	number	m²	Walls (+ ceiling) − openings.
`area_ft2`	number	ft²	Area in square feet.
`sheets_needed`	integer		ceil(area × (1 + waste_percent/100) / sheet_area).
`sheet_size_used`	string		Board size assumed.
`screws`	integer		About 1 screw per ft² of board (≈ 32 per 4 × 8 sheet at 16 in stud spacing).
`joint_compound_liters`	number	L	Ready-mixed all-purpose compound: 37.8 L per 100 m² of board (USG).
`joint_compound_gallons`	number	US gal	10 gal per 1,000 ft² of board (USG).
`compound_pails_4_5_gal`	integer		ceil(gallons / 4.5), the common US pail size (about 17 L).

Example

15 ft × 12 ft × 8 ft room with ceiling, 4 × 8 sheets, 10 % waste: {"unit_system":"imperial","room_length":15,"room_width":12,"wall_height":8,"include_ceiling":true,"sheet_size":"4x8_ft","waste_percent":10} → {"area_ft2":612,"area_m2":56.86,"sheets_needed":22,"sheet_size_used":"4 × 8 ft","screws":612,"joint_compound_gallons":6.12,"joint_compound_liters":23.2,"compound_pails_4_5_gal":2}

40 m² of wall, 1200 × 2400 mm boards, 10 % waste: {"unit_system":"metric","wall_area":40,"waste_percent":10} → {"area_m2":40,"area_ft2":430.56,"sheets_needed":16,"sheet_size_used":"1200 × 2400 mm","screws":431,"joint_compound_liters":16.3,"joint_compound_gallons":4.31,"compound_pails_4_5_gal":1}

GET https://tttkmbb.com/api/v1/calculate/drywall?unit_system=imperial&room_length=15&room_width=12&wall_height=8&include_ceiling=true&sheet_size=4x8_ft&waste_percent=10

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/drywall (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/drywall · Markdown: https://tttkmbb.com/construction/drywall.md · JSON definition: https://tttkmbb.com/construction/drywall.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="drywall"
OpenAPI operationId: estimate_drywall_sheets
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

FAQ

Should I subtract doors and windows?

Usually not for standard openings: the cut-out pieces are rarely reusable, so most estimators ignore openings under about 2 m² and only deduct large ones via openings_area.

Which sheet size should I choose?

Use the longest sheets you can handle: 4 × 12 ft or 1200 × 3000 mm sheets reduce the number of joints to tape; 4 × 8 ft and 1200 × 2400 mm are the common DIY sizes.

Is tape included?

No. Joint tape is roughly 37 m per 100 m² (370 ft per 1,000 ft²) of board; corner bead is the sum of the outside-corner lengths.

Related calculators

Paint Calculator — Paint for the finished boards.
Wallpaper Calculator — Paper for the finished boards.