Estimate drywall sheets for walls, ceilings, or both — metric or imperial, with optional joint compound, tape, fasteners, weight and cost.
Surface
Calculation method
Sheet size presets are stored in their native unit and converted correctly regardless of which measurement unit you're using above — a 1200mm preset never becomes "1200 inches".
Waste varies with room geometry, openings, sheet orientation, cuts, damage and installer experience — there's no universally "correct" figure, so adjust this for your project.
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Written and reviewed by Mohsin Iqbal · Last reviewed August 2026
Use this drywall calculator to estimate sheets for walls and ceilings, including doors, windows and a waste allowance.
It can also be used as a sheetrock calculator or a gypsum board estimator by entering the exact sheet dimensions sold in your region, since the underlying math — area divided by sheet size, plus waste, rounded up — works the same regardless of what your local market calls the product.
Enter a simple room, or add custom wall sections for irregular layouts, then optionally add joint compound, tape, fasteners, weight and cost. It's a material-estimation tool, not a structural or code-compliance tool — see Limitations below.
Calculate the total wall and ceiling area, subtract doors and windows, divide the remaining area by the area of one drywall sheet, then add your chosen waste allowance and round up to whole sheets.
You can only buy whole sheets, so the final figure is always rounded up — never a fraction.
Net Area = (Wall Area + Ceiling Area) − Opening Area
Raw Sheets = Net Area ÷ Sheet Area
Final Sheets = ROUND UP[ Raw Sheets × (1 + Waste %) ]
This calculator uses an area-based estimate: it divides your total net drywall area by the area of a single sheet, then rounds up after adding waste.
It does not optimise actual sheet layout, orientation or cut pattern for individual walls or ceilings — real-world sheet count can be higher than this estimate because of stud/framing layout, ceiling direction, sheet orientation, seams, cutouts, staggered joints, room geometry, or damaged pieces during handling and installation.
For simple rectangular rooms this area-based figure is usually close to the true purchase quantity; for complex layouts with many openings or angles, choose a higher waste allowance to compensate.
Sheet Area = Sheet Width × Sheet Length
Raw Sheets = Net Surface Area ÷ Sheet Area
Final Sheets = ROUND UP[ Raw Sheets × (1 + Waste %) ]
This calculator supports walls only, ceiling only, or walls and ceiling together.
In Room mode, wall area is calculated from the room's perimeter and height, and ceiling area from length times width — both are calculated independently and only added together when you select "Walls + Ceiling", so switching modes never double-counts a surface.
In Custom Walls mode, since individual wall sections don't necessarily form a rectangular room, ceiling area (if included) is entered separately as its own length and width.
Wall Area (room) = 2 × Length × Height + 2 × Width × Height
Ceiling Area = Length × Width
Add up width times height for each wall you're covering, add length times width for the ceiling if it's included, then subtract the area of any doors and windows to get your net drywall square footage (or square metres, if you're working in metric).
This calculator performs that calculation automatically and displays the result in the unit you've selected.
Total Wall Area = Σ (Width × Height) per wall
Ceiling Area = Length × Width
Net Drywall Area = (Wall Area + Ceiling Area) − Opening Area
There's no single universal drywall or plasterboard sheet size — common sizes vary by region and product.
Common North American drywall sheet sizes include 4 × 8ft, 4 × 10ft and 4 × 12ft, while common metric plasterboard/gypsum board sizes include 1200 × 2400mm, 1200 × 2700mm and 1200 × 3000mm.
This calculator offers these as presets, but always lets you enter a custom sheet size, since sheet dimensions vary by manufacturer and market.
Sheet presets are stored in their native unit and converted correctly regardless of which measurement unit you have selected — a 1200mm preset is never misread as 1200 inches just because you switch the display unit.
Waste allowance covers the drywall lost to cuts, offcuts around openings, sheet orientation, seams and the occasional damaged sheet.
There's no universally "correct" waste percentage — it depends on room geometry, the number of openings, sheet orientation, cuts and your own experience level. This calculator offers 0%, 5%, 10% and 15% presets, plus a custom option.
Simple rectangular rooms with few openings typically need less waste allowance; rooms with many doors, windows, angles or a complex ceiling generally need more.
The optional drywall mud calculator in the Mud, Tape & Fasteners tab estimates joint compound containers from your net drywall area.
Compound usage depends on the number of joints, number of finishing coats, corner beads, workmanship and the specific product's yield, so there's no single number that fits every job and no universal container size.
Enter the coverage figure from your specific product's manufacturer information — this calculator never claims an exact bag or bucket quantity, and never fills in an arbitrary coverage figure for you.
Compound Containers = ROUND UP( Net Drywall Area ÷ Coverage per Container )
Tape is calculated separately from a total joint length you enter (measured or estimated) divided by your tape roll length, since this calculator doesn't model exact seam layout closely enough to calculate joint length automatically from sheet count alone.
Tape Rolls = ROUND UP( Total Joint Length ÷ Roll Length )
The optional cost calculator estimates material cost using your own local prices for sheets, joint compound containers, tape rolls and fastener boxes, in USD, GBP, EUR, AUD, CAD or NZD.
This calculator doesn't publish or assume market prices, since they vary by region, product and supplier — enter your own prices for an estimate.
The cost estimate covers materials only; it excludes labour, delivery, framing, insulation, paint, corner bead and tools unless you price them separately.
| Step | Working | Result |
|---|---|---|
| Room | 4m × 3.5m, wall height 2.4m, walls only, sheet 1200 × 2400mm, 10% waste | — |
| Wall area | 2×4×2.4 + 2×3.5×2.4 | 36.00 m² |
| Sheet area | 1.2 × 2.4 | 2.88 m² |
| Raw sheets | 36.00 ÷ 2.88 | 12.500 |
| +10% waste | ROUND UP(12.500 × 1.10 = 13.750) | 14 sheets |
| Step | Working | Result |
|---|---|---|
| Room | 12ft × 10ft, wall height 8ft, walls + ceiling, sheet 4 × 8ft, 10% waste | — |
| Wall area | 2×12×8 + 2×10×8 | 352.0 ft² |
| Ceiling area | 12 × 10 | 120.0 ft² |
| Gross area | 352.0 + 120.0 | 472.0 ft² |
| Sheet area | 4 × 8 | 32 ft² |
| Raw sheets | 472.0 ÷ 32 | 14.750 |
| +10% waste | ROUND UP(14.750 × 1.10 = 16.225) | 17 sheets |
| Step | Working | Result |
|---|---|---|
| Walls | 5m × 2.4m + 4m × 2.4m, one door 0.9 × 2.1m, one window 1.2 × 1.2m, sheet 1200 × 2400mm, 15% waste | — |
| Gross wall area | (5×2.4) + (4×2.4) | 21.60 m² |
| Openings | (0.9×2.1) + (1.2×1.2) | 3.33 m² |
| Net area | 21.60 − 3.33 | 18.27 m² |
| Raw sheets | 18.27 ÷ 2.88 | 6.344 |
| +15% waste | ROUND UP(6.344 × 1.15 = 7.295) | 8 sheets |
Every worked example above was run through the calculator's actual formula before publishing, so entering the same figures into the calculator will reproduce these results exactly.
Drywall is the generic term most commonly used in the United States and Canada for gypsum-cored interior wall and ceiling panels.
Sheetrock is a well-known brand name that's often used conversationally as a generic term for drywall in the US — this calculator uses the term descriptively and isn't affiliated with any brand.
For material estimation, use the actual width and length of the sheet product you plan to buy. Gypsum board is the technical, generic product term used across regions and industry documentation.
Plasterboard is the common everyday term in the UK, Australia and New Zealand for the same general category of product, and Gyprock is a widely recognised Australian brand name sometimes used conversationally in the same way as Sheetrock.
Whatever term your region or supplier uses, this calculator works the same way — just enter the actual sheet dimensions for the product you're using.
This calculator is a material-quantity estimator. It calculates net area, sheet count, and optional joint compound, tape, fastener, weight and cost estimates from the dimensions and rates you enter.
It does not determine required board type, fire rating, moisture resistance, acoustic specification, framing requirements, fastener spacing/pattern, or building-code compliance. The sheet-count formula is area-based and does not optimise actual sheet layout, orientation or cut pattern — real material usage can be higher due to stud/framing layout, ceiling direction, sheet orientation, seams, cutouts, staggered joints, room geometry, or damaged pieces during handling and installation.
Joint compound and tape figures are planning estimates based on the coverage rate, joint length and roll length you enter, not exact quantities.
Cost estimates use only the prices you enter and exclude labour, delivery, framing, insulation, paint, corner bead, tools and tax unless you price them separately.
Follow your product's manufacturer guidance, building plans and local building regulations for board type, fire rating, moisture resistance, acoustic requirements, framing and fastener specifications.
Calculate the total wall and/or ceiling area, subtract doors and windows, divide the remaining area by the area of one drywall sheet, then add your chosen waste allowance and round up to whole sheets.
Enter your own room or wall dimensions above for an exact figure.
Add up width times height for each wall, add length times width for the ceiling if you're covering it, then subtract the area of any doors and windows.
This calculator does that math for you and also converts the total into sheets and, if you switch units, into square metres.
Divide your net wall and/or ceiling area by the area of one drywall sheet, add your waste allowance, then round up to a whole number — you can only buy whole sheets.
The exact count depends on your sheet size and waste percentage, so enter your own figures above rather than relying on a single rule of thumb.
Select "Walls + Ceiling" in the calculator above to combine wall area and ceiling area (length times width) into one net area, then the sheet count is worked out from that combined total.
Switching between walls only, ceiling only, and walls plus ceiling never double-counts a surface.
Common North American sheet sizes are 4 × 8ft, 4 × 10ft and 4 × 12ft, while common metric plasterboard/gypsum board sizes include 1200 × 2400mm, 1200 × 2700mm and 1200 × 3000mm.
There's no single universal size, so this calculator lets you pick a common preset or enter your own sheet dimensions.
Joint compound usage depends on the number of joints, number of finishing coats, corner beads and your own workmanship, so there's no single figure that fits every job.
Enter your net drywall area and the coverage rate from your specific product's manufacturer information in the Mud, Tape & Fasteners section — there's no universal container size or coverage figure this calculator can supply for you.
This calculator estimates joint compound containers by dividing your net drywall area by the coverage rate you enter from your specific product's manufacturer information.
It's a planning estimate, not an exact quantity, since compound usage varies with joints, coats, finishing level and technique — there's no universal coverage figure this calculator fills in automatically.
There's no universally correct waste percentage — it depends on room geometry, the number of openings, sheet orientation, cuts and your own experience level.
This calculator offers 0%, 5%, 10% and 15% presets plus a custom option, since simple rectangular rooms typically need less waste allowance than rooms with many openings or angles.
Sheetrock is a brand name commonly used conversationally for drywall in the United States. For material estimation, use the actual width and length of the sheet product you plan to buy.
Plasterboard is the common term used in the UK, Australia and New Zealand for the same general type of gypsum-cored sheet material called drywall in North America.
The underlying calculation — area divided by sheet size, plus waste — works the same either way, so this calculator supports both terms and both metric and imperial sheet sizes.
Yes, for a more accurate material estimate — enable openings in the calculator above and enter the width, height and quantity of each door and window.
Subtracting openings reduces your net area and therefore your sheet count; if you skip this step, the calculator will slightly overestimate how much drywall you need.
This calculator can estimate total fastener count if you enter your own fasteners-per-sheet rate, but it doesn't prescribe fastener spacing or pattern, since required screw spacing depends on framing type, ceiling versus wall application, board thickness, local building code and manufacturer requirements.
Check your project's specification or local code for the correct fastening pattern.
Gypsum board is the technical, generic product term for the gypsum-cored panel material that's commonly called drywall in North America, plasterboard in the UK/Australia/New Zealand, and sometimes Sheetrock or Gyprock conversationally after well-known brand names.
They all refer to the same general category of product for calculation purposes.
No — sheet count depends on the area you're covering and the sheet's width and length, not its thickness.
Thickness affects weight, fire rating, sound performance and cost per sheet, which is why this calculator only asks for thickness-related figures if you're using the optional weight or cost estimate.