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Renovation & Construction

Drywall Calculator

Estimate how many drywall sheets, screws, and how much joint tape you need for a room, based on wall area and a standard waste allowance.

Drywall is plasterboard in the UK and Australia.

  • Answers as you type
  • Every formula cited
  • Calculated in your browser
SettingsSettings for this calculationUS
Market
Imperial · sales tax
Who is doing the work?

The standard allowance most suppliers and estimating guides assume for ordinary work.

Board a whole rectangular room, a stretch of wall, or a face you already know the area of.

Sheets are counted from the face these give. An L-shaped room or a single partition is a stretch of wall; a gable, a stair wall or anything off a drawing is easiest as its area.

The length of the room, wall to wall.

Measure along the floor from one wall to the opposite wall.

Tools needed: Tape measure or laser measure

The width of the room, wall to wall.

Measure along the floor perpendicular to the length.

Tools needed: Tape measure or laser measure

Floor-to-ceiling height.

Standard residential ceilings are commonly 2.4 m (8 ft); measure yours if it might differ.

Tools needed: Tape measure or laser measure

Door openings don't need drywall.

Count the door openings in the walls being boarded. Each one takes off the area of one door, set further down.

Window openings don't need drywall.

Count the window openings in the walls being boarded. Each one takes off the area of one window, set further down.

What each door opening takes off the boarded area. The default suits a standard interior door with its frame.

The default is the allowance estimators use for a standard interior door opening. A double door, a wide cased opening or a door to a garden takes off more: measure the opening and enter its width times its height. With openings of different sizes, enter their average — the total taken off is then exact.

What each window opening takes off the boarded area. The default suits a typical window.

The default is a typical window opening's allowance. A picture window or a sliding patio door takes off far more, and a small landing window less: measure the opening and enter its width times its height. With windows of different sizes, enter their average — the total taken off is then exact.

Extra material for cuts, mistakes, and irregular walls.

10% is standard for simple rectangular rooms. Use 15% for rooms with many corners, angles, or a ceiling install.

Estimated drywall needed

12 sheets (4x8 ft)

High confidence
Gross wall area
392 sq ft
Doors + windows area (subtracted)
51.13 sq ft
Net wall area
340.87 sq ft
Area with waste factor
374.96 sq ft
Joint tape needed
126.12 linear ft
Drywall screws needed
384 screws
Then change the inputs to see how far the answer moves.

Show calculation logic

How this was calculated

Formula source(s)

  • Standard drywall sheet size is 4 ft x 8 ft (32 sq ft / 2.973 m²) in North America and 2400 x 1200 mm (2.88 m²) in metric markets — the most common sizes sold for wall installation
  • 10-15% waste factor is standard industry practice for rooms with doors, windows, and outlet cutouts
  • Joint tape: approximately 370 linear ft per 1,000 sq ft of drywall area (common manufacturer/retail estimating rule); screws: approximately 32 per standard sheet — 4x8 ft or 2400x1200 mm, within 3% of each other in area — on 16 in o.c. framing

Inputs used

Walls to Board
Four walls of a rectangular room
Wall Length to Board
49 ft
Board Height
8 ft
Face Area to Board
390 sq ft
Room Length
13 ft
Room Width
11.5 ft
Wall Height
8 ft
Number of Doors
1
Number of Windows
2
Area of One Door
20.99 sq ft
Area of One Window
15.07 sq ft
Waste Factor (%)
10

Intermediate steps

Gross wall area
392 sq ft
Doors + windows area (subtracted)
51.13 sq ft
Net wall area
340.87 sq ft
Area with waste factor
374.96 sq ft
Joint tape needed
126.12 linear ft
Drywall screws needed
384 screws
Final result12 sheets (4x8 ft)

What this calculation does not cover

  • One area stands for every door and one for every window, so a room with a sliding patio door and a small landing window takes the same off the boarding for each; enter the average of the openings a field stands for and the total taken off is exact, though no single wall's share is.
  • That deduction is taken before the waste factor is applied, so the board cut out of a doorway or a window head is treated as material recovered elsewhere on the job, and the reveals returning into each opening are subtracted here rather than added even though they still have to be boarded and finished.
  • Measured as a room, the wall area is 2 × (length + width) × height — one closed rectangle at a single height — so a chimney breast, an alcove, a stub partition or a closet wall standing inside the room adds boarded surface the perimeter never sees; give those as a run of wall or as a measured area instead. The ceiling is never part of it.
  • The sheet figure is an area division, waste-loaded area over one board's area (2.973 m² for a 4x8 ft sheet, 2.88 m² for a 2400x1200 mm one) rounded up once at the end, which assumes one board size, one layer, and offcuts used down to the last piece rather than a hanging plan; 12 ft boards, short 1800x900 boards or a double-layer partition all give a different count.
  • Screws are simply 32 per sheet, the figure quoted for framing at 16 in centres, so the total does not move for 24 in or 600 mm centres, for metal furring or resilient bar, or for the tighter pattern a ceiling install takes — and since it multiplies the waste-loaded sheet count, whatever waste percentage you chose is carried into the screw number too.
  • Joint tape is a flat 0.37 linear ft per square foot of net wall area, an average that knows nothing about your joint layout: boards hung vertically in a tall room, or a wall broken into short runs, generate more joint per square metre than that average assumes, and corner bead and the compound that fills the joints are outside this figure entirely.

Estimated cost — your price

This site holds no price list for this material — local prices vary too much to publish honestly. Enter your supplier's price and the result is costed with it.

Schematic layout — positions are illustrative, quantities are exact. This calculator is told how many doors and windows there are, never where they sit or how big each one is, so they are drawn evenly spaced at the standard allowance it deducts. Moving one would change nothing in the numbers above.

Plan of Room, 13′ by 11′ 6″, with 1 door(s) and 2 window(s), positions shown schematically.13′11′ 6″1′

Part of bigger jobs

This trade is one line of several job takeoffs. Run the whole job and every other trade comes back with it, off the same measurements.

Or plan the space itself: measure it once, doors and windows included, and this figure comes back worked out on that space, with what goes with it.

Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.

Sources checked 2026-09-17 · v1.2.0

Regulatory standards & verification citations3
  1. Standard drywall sheet size is 4 ft x 8 ft (32 sq ft / 2.973 m²) in North America and 2400 x 1200 mm (2.88 m²) in metric markets — the most common sizes sold for wall installation
  2. 10-15% waste factor is standard industry practice for rooms with doors, windows, and outlet cutouts
  3. Joint tape: approximately 370 linear ft per 1,000 sq ft of drywall area (common manufacturer/retail estimating rule); screws: approximately 32 per standard sheet — 4x8 ft or 2400x1200 mm, within 3% of each other in area — on 16 in o.c. framing
Cite this page

Your workspace

Most jobs need more than one number. Add the calculators you need next and they open right here, underneath this one — your figures stay on screen and nothing is lost to a page change.

Tools and safety for this job

To hang plasterboard and cut board around openings and boxes. Generic types, no brands, no prices.

Protection this work requires

  • Joint-compound dust is very fine and travels: a P1/FFP1 mask is the minimum, and a damp-sponge finish avoids most of it.
  • Boards, blocks and bagged material cause most lasting back injuries on small sites: two people or a lifter for full sheets, and never a bag on one shoulder up a ladder.
  • Knives cause more site injuries than any power tool: cut away from your body, change blades often, and wear cut-resistant gloves to EN 388 level C for repeated cutting.
Show the 9 tools this job needs

Essential

  • Cordless drill/driver

  • Drywall saw

  • Tape measure

  • Utility knife

Recommended

  • Board lifter

  • Combination or framing square

  • Drywall screw gun

Optional

  • Oscillating multi-tool

  • Panel lift

Also needed as materials: drill and driver bits, oscillating blades, replacement blades.

what each drywall tool is for, and the spec that decides which to buy where one does.

Now that you have the number

These guides cover the work this quantity is for — the first ones run this calculator inside the section that raises the question.

  • Fixing Heavy Things to a Plasterboard Walluses this calculator

    A 40 kg screen on a swung-out arm is a lever, not a weight — so this is about reaching timber, rating a cavity fixing, or letting a pattress in.

  • Hanging Drywalluses this calculator

    Hanging drywall as a chain of decisions — board direction, joint placement, fastener depth — and what each one costs the finisher later.

  • Taking Off Quantities From a Drawing Setuses this calculator

    A plan set describes a finished building, never a delivery. The sweep that turns fourteen PDF sheets into an order a merchant can actually pick.

Called something else where you work? Plasterboard / drywall · Skim coat / joint compound — the term in each market, how close the equivalence really is, and the standard that governs it.

Still deciding? Drywall Ceiling vs Drop Ceiling · Three-Coat Plaster vs Drywall — the factors that actually differ, with no invented prices.

Already have some? How big a room will my drywall sheets board?

Worked examples: Bathroom gutted and retiled — step 9 of 9 · Basement room drywall — step 3 of 10 · Stud partition with a door — step 2 of 10

Worked for these jobs: A rectangular room's walls, in sheets · A bedroom reboarded, in plasterboard sheets

The data behind it: Production rates by operation

How to calculate drywall in 13 steps

  1. Walls to BoardBoard a whole rectangular room, a stretch of wall, or a face you already know the area of.
  2. Wall Length to BoardEvery wall being boarded, end to end, added up.
  3. Board HeightFrom the floor to the ceiling line the board stops at.
  4. Face Area to BoardThe wall face to cover, with its doors and windows still in it.
  5. Room LengthThe length of the room, wall to wall.
  6. Room WidthThe width of the room, wall to wall.
  7. Wall HeightFloor-to-ceiling height.
  8. Number of DoorsDoor openings don't need drywall.
  9. Number of WindowsWindow openings don't need drywall.
  10. Area of One DoorWhat each door opening takes off the boarded area. The default suits a standard interior door with its frame.
  11. Area of One WindowWhat each window opening takes off the boarded area. The default suits a typical window.
  12. Waste Factor (%)Extra material for cuts, mistakes, and irregular walls.
  13. Read the resultThe tool computes the result from those figures and shows the formula, its sources, and a confidence rating alongside it.

Frequently asked questions

Does this include the ceiling?
No — this estimates wall sheets only. Measure the ceiling separately and divide it by one sheet's area — 32 sq ft for a 4x8 ft sheet, 2.88 m² for a 2400x1200 mm one — if you're drywalling the ceiling too.
Why round up to whole sheets?
Drywall is sold in full sheets — you can't buy a fraction of one, so the estimate always rounds up.
What waste factor should I use?
10% for a simple rectangular room, 15% for rooms with lots of corners, angles, or if this is your first drywall job.
Does this account for a specific drywall thickness?
No — sheet count depends only on area covered, not thickness. Thickness (e.g. 1/2 in vs 5/8 in, or 12.5 mm vs 15 mm in metric markets) affects weight and fire rating, not how many sheets you need.
What about joint compound (mud)?
This page leaves it out, because mud coverage depends on the number of coats and the finish level, which the dedicated Drywall Joint Compound Calculator takes as inputs of its own. Those deserve dedicated inputs rather than a rough add-on here.
Preliminary estimate, not certified engineering. This tool produces an indicative quantity calculation for planning purposes only — it is not a certified structural analysis, a guaranteed material takeoff, or a substitute for building department approval. Always verify measurements on-site and have a licensed contractor or structural engineer review any load-bearing, code-sensitive, or safety-critical work before purchasing materials or starting construction. Spotted an arithmetic or standards error? Report it to contact@craftquantities.com with your inputs — a confirmed fix gets a permanent check of its own, so the same mistake cannot come back.