Drywall Calculator
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About the Drywall Calculator
Drywall is cheap; trips back to the store mid-hang are not. The estimate is simple area math with two judgment calls — whether the ceiling is included, and how much cut waste your room's shape will generate. Simple rectangular rooms waste about 10%; rooms with many openings, angles, or heights waste 15% or more.
Enter the room dimensions, choose walls-only or walls-plus-ceiling, pick your sheet size, and the calculator returns the sheet count plus the finishing materials. Longer sheets (4×10, 4×12) mean fewer joints to tape — the finishing time saved usually beats the awkwardness of handling them, if your access allows it.
Hanging is half the job — plan the finish coat with the Paint Calculator
The Sheet-Count Math
Perimeter method — fast and reliable for rectangular rooms:
Wall area = 2 × (length + width) × height Ceiling = length × width (if included) Sheets = ceil( area × (1 + waste%) ÷ sheet area ) (4×8 = 32 ft², 4×10 = 40 ft², 4×12 = 48 ft²)
Worked example: a 12 × 12 ft room with 8′ ceilings has 2 × 24 × 8 = 384 sq ft of wall; with 10% waste that's 422 sq ft → 14 sheets of 4×8. Adding the 144 sq ft ceiling brings it to 19 sheets.
Sheets for Common Rooms
4×8 sheets, 8′ ceilings, 10% waste — computed by this calculator:
| Room | Walls only | Walls + ceiling |
|---|---|---|
| 10 × 10 ft | 11 sheets | 15 sheets |
| 12 × 12 ft | 14 sheets | 19 sheets |
| 12 × 16 ft | 16 sheets | 22 sheets |
| 15 × 20 ft | 20 sheets | 30 sheets |
Ceilings in 12′-wide rooms are the classic case for 4×12 sheets: one sheet spans the room, cutting the joint count dramatically.
Screws, Tape & Compound
The industry estimating rules this calculator applies: screws at roughly 1 per square foot (a 4×8 sheet takes ~32 with 16″ o.c. framing); paper joint tape at about 37 linear feet per 100 sq ft of board; and ready-mix all-purpose compound at one 4.5-gallon bucket per ~450 sq ft for a full three-coat finish. Buy screws by the pound-box — a small box short is another store trip.
Type matters more than brand: ⅝″ Type X where fire code requires it (garages, between units), moisture-resistant board for baths and laundry, and standard ½″ everywhere else. Compound: setting-type (bag) mud for the tape coat resists shrinkage; ready-mix for fill and finish coats sands easier. None of that changes the counts — only what you're buying.
Frequently Asked Questions
How many sheets of drywall for a 12x12 room?
With 8′ ceilings: 14 sheets of 4×8 for the walls (384 sq ft + 10% waste), or 19 including the ceiling. Taller ceilings and busier room shapes push it up — the calculator adjusts for both.
Should I subtract doors and windows?
Generally no — the piece you cut out for an opening is rarely reusable elsewhere, so subtracting openings systematically under-buys. For a wall that's mostly glass (patio sliders), subtract that one opening manually and keep the waste factor for the rest.
How many screws per sheet of drywall?
About 32 per 4×8 sheet on 16″ on-center framing — screws every 12″ in the field and 8″ on edges works out to roughly one per square foot of board, which is the rule this calculator uses.
How much joint compound do I need?
Rule of thumb: one 4.5-gallon bucket of ready-mix per ~450 sq ft of hung board for the full tape-fill-finish sequence. Textured finishes and level-5 skim coats need substantially more; smooth-wall pros often mix setting compound for the first coat.
Which sheet size should I use?
The longest you can physically get into the room and lift: 4×12 sheets mean up to a third fewer joints than 4×8 — and finishing joints, not hanging board, is where drywall time goes. Solo hangers and tight stairwells are what 4×8s are for.
Do I hang the ceiling or walls first?
Ceiling first — wall sheets then support the ceiling board's edges, hiding and stiffening the perimeter joint. If you're doing both, note the calculator's walls+ceiling option counts the board; the sequence is on you.
Methodology. This calculator uses standard construction and material-estimation formulas. It is reviewed and maintained by the Vast Calculators editorial team.
Last updated · July 2026
Results are estimates for general use; verify critical figures independently.