Drywall and plasterboard: sheets, fixings, finishing and the framing behind them

What the drywall calculators cover

A drywall job is more than a sheet count. This page lists the calculators in the order the work runs: the board, the fire-rated and shaft wall systems, the fixings, the joint finish, the metal frame behind the board, suspended ceilings, sound detailing and the weight of what is thrown away. Each one says what its answer rests on, and where a published document sets a figure the page names the document instead of restating the figure as the site's own.

The first group counts whole sheets for walls and ceilings, with the openings taken off, the board that wraps a boxed-in soffit added, and access panel cut-outs deducted. The reverse calculator starts from the sheets you hold and gives the area they will cover, and two converters turn an area into sheets and a sheet count back into an area, so a delivery can be checked against a take-off.

Fixings are counted from the schedule rather than the area: screws round the edge and across the field of each sheet, ceiling screws on a tighter grid, adhesive cartridges at a bead size, and the screws that fix resilient sound clips. Finishing is counted from lengths: tape from the sheet layout and the angles of the room, bead from the outside corners, trim from the exposed edges and backing behind the butt joints. The last group converts board waste between weight and volume for disposal.

How the answers are worked out

The drywall calculator uses the sheet size of the market: one module in North America and another in metric markets, within a few percent of each other in area, which is why a count can change when the unit system does. The waste factor is an input, the count is rounded up to whole sheets, and the tape and screw figures come from stated rules of thumb. The screw calculator works from the sheet's own geometry instead, counting the screws round the perimeter at one spacing and the screws across the field at another.

Joint compound is where figures differ most, and the finish level calculator says why. It applies the coat counts of GA-214 level by level and the joint treatment of ASTM C840, then multiplies the joint lengths by a quantity of compound per metre that the page labels a rule of thumb, with a separate rule-of-thumb allowance for the skim coat of the top level. The compound calculator is the quicker figure and says that its box covers a stated area for a full three-coat finish, on common manufacturer sheets, and that the box is a North American product.

Two pages say outright what they do not decide. The fire-rated layer calculator counts sheets for the layers you give it, and states that the number of layers a rating needs must come from a tested UL or GA assembly design and not from a formula. The sound estimator is described as an additive rule of thumb, not an ASTM E90 rating, and it is an indication only.

Units and documents by market

The market setting chooses the system the answers appear in: inch-pound units for the United States, metric for the United Kingdom, Australia and Canada, with every calculator restating its answer in the other. The site's market notes also name the product: drywall in the United States and Canada, plasterboard in the United Kingdom and gyprock in Australia. This page says drywall throughout and carries the other names in its heading. The table shows which documents the calculators cite for each market.

The frame and the ceiling behind the board

The metal framing pages count studs at the chosen centres, both end studs included, and track from the wall run. They cite AISI S100 and the IBC for cold-formed steel, and the shaftwall limiting height page is a check of a published figure and not a sizing. The suspended ceiling pages count a grid from the room: the drop ceiling calculator cites manufacturer installation instructions and merchant listings from both the United States and the United Kingdom, so its main beams, cross tees and wall angle are counted in each market's stock lengths.

Order matters on a ceiling as much as on a wall. The tile calculator sets out a grid so that the border panels fall between half a panel and a whole one, the hanger calculator counts wires from a grid spacing, and the control joint calculator counts the joints a board ceiling needs within a maximum unbroken run.

What the calculators leave to others

A fixing schedule belongs to the board and the framing it is fixed to, and the screw calculators take the spacing as an input rather than assume it. Adhesive quantities follow the bead size and the spacing that the adhesive's maker and GA-216 set, and the calculator says so. Every figure here is a quantity to order from, and the assembly drawings, the tested system and the supplier's data govern.

Whole jobs, taken off

A job takeoff asks for the dimensions once and returns every line the job needs, each from its own calculator. These are the ones where drywall is a main line.

• Room fit-out

  A rectangular room boarded, filled, painted and floored from one set of dimensions, the board being the first line.

• Drywall ceiling

  A flat plasterboard ceiling: boards, screws, tape, compound and control joints from the room's two dimensions.

• Stud partition

  A single run of internal partition: the studs, the jointing compound and the outlets.

• Suspended ceiling grid

  A lay-in grid ceiling: tiles, hanger wires, wall angle and runner splices.

• Party wall soundproofing

  A shared wall lined against a neighbour's noise, where the board is one layer in a decoupled build.

• Basement or cellar conversion

  A cellar made habitable, with the boarding of its new walls one step among the damp and insulation work.

Read an answer backwards

When you start from what you hold and want to know what it will cover, these pages run the same calculators in reverse.

• How big a room will my drywall sheets board?
• How big a room will my drop ceiling tiles cover?
• How big a ceiling will my plasterboard sheets cover?
• How long a fire-rated wall will my Type X sheets board?

Worked examples

A job worked through with its inputs and its working shown, so you can see the figures before you enter your own.

• Basement room drywall

  A basement room boarded from the studs to the finished joint, with the board, fixings and compound bought in turn.

• Stud partition with a door

  A partition framed and boarded with a door in it, so the opening's deduction is worked rather than assumed.

• A rectangular room's walls, in sheets

  Drywall for the walls of a 12 by 10 ft room with 8 ft walls

• A bedroom reboarded, in plasterboard sheets

  Plasterboard for the walls of a 4.2 by 3.3 m bedroom

Reference tables

• Production rates by operation

  How long each operation takes one person, in person-hours per unit of work.

Guides

The practice behind the numbers: how the work is done, what goes wrong and how to check it.

• Hanging Drywall

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

• Taping and Finishing to a Level

  Levels 0 through 5 are a ladder of coats and scrutiny: what each rung costs, what light exposes, and where a specification should stop.

• Drywall Finish Levels and What Each One Costs in Compound

  Below Level 5 compound is bought along the seams; at Level 5 it is bought over the whole wall. That change of unit, not extra care, is what doubles the order.

• Taking Off Board for Shafts, Soffits and One-Sided Walls

  A riser priced as a two-sided partition buys twice the board, misses the liner completely, and never checks whether the stud height works.

• Framing a Cold-Formed Steel Partition

  A tall steel partition decided the way it fails: section against the movement limit first, then the fastener counts that fall out of it.

• Building a Rated Shaftwall

  Shaftwall is the one rated assembly built entirely blind — every panel, stud and screw has to land from the corridor side alone.

• Putting Boxes and Joints Into a Fire-Rated Wall

  A rated partition carries a fixed allowance of openings and one moving joint at its head, and two trades spend it without ever seeing each other's tally.

• Stopping Sound Through a Partition: Mass, Gaps and Decoupling

  The open-area budget a partition gets to spend, what a doubling of board actually buys, and why the door decides the number.

• Isolating Sound Through a Partition

  A path-by-path hunt for flanking on a separating wall, from the perimeter bead to the plenum, before anyone argues about board.

• Fixing Heavy Things to a Plasterboard Wall

  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.

• Dry-Lining a Solid Wall

  Dabs or a furring grid on a solid masonry wall: what the substrate decides, and why each route hands the estimator a different thing to count.

• Hanging a Suspended Ceiling

  A suspended ceiling is a grid borrowed from structure that never expected it — work upward from tile face to hanger wire to deck.

• Detailing a Large Ceiling

  A big ceiling is decided at its edges and its breaks: where the run is interrupted, and how much perimeter trim is ordered before boarding starts.

• Building a Curved Drywall Wall

  A radius partition set out, framed, kerfed and beaded by one piece of arithmetic: how far a chord sags away from the arc it spans.

• Overboarding or Taking Down a Lath and Plaster Ceiling

  Two answers to a bowing Victorian ceiling — board over it or take it out — and the screw length, dust and container size that decide which.

Terms

• Plasterboard / drywall
• Dry lining and drywall installation
• Skim coat / joint compound
• Stud and framed partition
• Suspended ceiling
• Firestopping and cavity barriers
• Sound insulation ratings
• Impact sound insulation
• Sealant and caulk
• Lath and plaster background
• Subfloor
• Tolerance and permitted deviation

How the numbers are worked out

Every calculator names the method it uses and the standard or guidance behind it. These are the methods the most of the calculators above rest on, and the published documents they cite.

Methods

• Quantity, Waste and Rounding

  Why a material count is a ceiling function rather than a division, and why the waste factor — not the geometry — carries the risk. Applies to 16 of the calculators above.

• Sound Transmission, Flanking and the Weakest Path

  Why one per cent of open area destroys an otherwise excellent wall, why doubling the mass buys only six decibels, and why an isolator with too little deflection makes vibration worse rather than better. Applies to 6 of the calculators above.

• Spacing, Pitch and the Count That Follows

  Why a run divided by a spacing gives the number of gaps and not the number of things, why the division rounds up rather than to nearest, and what the leftover bay at the end does to both. Applies to 6 of the calculators above.

• Perimeter Runs, Stock Lengths and Mitres

  Why a room's area tells you nothing about how much skirting it needs, why adding a door can increase the trim order, and why a crown moulding mitre is neither forty-five degrees nor half the corner angle. Applies to 5 of the calculators above.

• Coverage Rate and Spread

  How a datasheet figure becomes an order quantity, why it is quoted per coat and calculated for a smooth plane, and what a real substrate does to it. Applies to 3 of the calculators above.

• Rolls, Sheets and the Lap Between Them

  Why covering an area with rolls is a strip count rather than a division, why the lap is bought twice over, and why turning the strips the other way can change the order. Applies to 3 of the calculators above.

Standards cited

• International Building Code

  United States. Cited by 1 of the calculators above.