Drywall Calculator
Sheets, mud, tape and screws for walls and ceilings — the finishing chain priced off one area.
Drywall Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Rectangular rooms; vaults and soffits add by hand.
- One door and window size each — customs by hand.
- No texture or Level 5 skim gallons.
In short: A 12 × 12 room, 8-ft walls, one door, one window: 492 ft² → 18 sheets of 4×8 at the blended waste (walls 10%, ceilings 14%), 6 gal of mud (280 ft²/gal × 3 coats), 5 rolls of tape, 528 screws.
Formula
area = 2(L+W)×H − 21/door − 15/window (+ L×W ceiling)
sheets = ⌈area × (1 + waste) ÷ ft²/sheet⌉
mud = ⌈area × 3 coats ÷ 280⌉ gal
screws = ft² × 1.0 wall / 1.25 ceiling
[('32 ft²', 'the 4Ð8 sheet — 40 and 48 exist to kill seams'), ('280', 'ft² per gallon-coat of compound, USG'), ('500 lf', 'paper tape per 100 ft² of board'), ('1.25', 'ceiling screws per ft² — the C840 premium')]
Worked Example
- Take off the walls, out the openings, in the ceiling.
- Sheet it at 32 ft² with the waste mix.
- Chain the mud: three coats at 280 per gallon.
- Tape at 500 lf per hundred; screws by the surface mix.
- Order from one mill run — paper tone varies.
The 12 × 12 room at 8 ft: 384 gross − 36 openings = 348 walls + 144 ceiling = 492 ft² → 18 sheets at the 11.2% blended waste; mud 6 gal; tape 5 rolls; screws 528. The finishing chain is where the money hides.
Strengths & Limits Of This Model
Where this engine is strong
- The mud chain priced, not waved at
- Ceiling premium in waste AND screws
- Sheet size trade-off visible
Where it stops
- Standard opening sizes only
- No texture materials
Practical Use Cases
Room finishing
Sheets to screws in one pass.
Basement builds
Partition walls plus ceilings.
Sheet choice
4Ð8 vs long sheets on tall walls.
Mud orders
Gallons for a real Level 4.
Contractor checks
Counts against the bid’s lines.
Methodology & Editorial Standards
Area is perimeter × height minus fixed 21/15 ft² opening deductions, plus the ceiling at L×W when included. Sheets ceil area over the chosen sheet with a blended waste (10% walls, 14% ceilings). Mud chains at 280 ft² per gallon-coat × 3; tape at 500 lf per 100 ft²; screws at 1.0/1.25 by surface. Openings never go negative.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
Drywall Calculator — 10 Expert FAQs
10 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How many 4x8 sheets do I need for a 12x12 room?
348 ft² of walls after one door and one window, 492 with the ceiling — 18 sheets of 32-ft² board at blended waste. Long sheets change seams, not the area law.
How much joint compound per square foot?
A gallon spreads about 280 ft² PER COAT, and a paint-ready Level 4 is three coats — call it a gallon per 93 ft² of finished board. The 12 × 12 room wears six gallons.
How many drywall screws per sheet?
About 32 in a 4Ð8 on walls (1.0 per ft²), 40 in ceilings (1.25) where screws run 12 in on joists per ASTM C840. A 500-screw pound covers roughly 500 ft² of wall.
Should I deduct doors and windows?
Yes — 21 ft² per standard door, 15 per window. The rounding waste mostly absorbs what the openings’ cut edges cost, so the deduction is honest, not optimistic.
When do 4x10 or 4x12 sheets pay?
Nine- and ten-foot walls, and ceilings — one long sheet replaces a seam’s tape, mud and sanding. They cost more per board and two people to hang; on tall walls they win.
How much waste should drywall carry?
10% on straightforward walls, 14% on ceilings, more on vaults and angles. Offcuts never fit the next opening as neatly as the plan drew them.
What is a Level 4 finish?
Tape embedded, two additional coats over flats and one over corners, sanded — the standard under flat or eggshell paint. Level 5 adds a skim coat for gloss paint or critical light.
Do ceilings really take more screws?
Yes — 12-in spacing on joists versus 16 on studs puts 1.25 screws per square foot overhead, because gravity works all night. The page carries the premium automatically.
How much does hung drywall cost per square foot?
Installed rates vary by region and ceiling height — this page prices MATERIALS on your quotes and leaves labor to your market. Hanging and finishing run several times the board cost.
Why buy all sheets from one run?
Paper color and surface tone vary by mill run — mixed batches telegraph through thin paint. One run, stacked flat, stored dry.