How to estimate drywall sheets from plans

A drywall estimate comes down to one number: total board area, divided by the area of one sheet, plus waste. The work is in getting the board area right — every wall, every side, every layer.

1. Measure the linear feet of each wall type

Go through the floor plan and total the length of every wall, grouped by wall type (the tag that points to the wall-type legend). Different types often mean different board: 5/8" Type X on rated walls, moisture-resistant board in wet areas, two layers on some partitions.

2. Multiply by the board height

Wall area = linear feet × height. Use the height the board actually runs — to the ceiling, or full height to the deck above if the wall-type detail says so. That detail matters: a wall that runs to the deck can be 30–50% more board than one that stops at the ceiling.

3. Count sides and layers

• An interior partition usually has board on both sides — double the area.
• An exterior wall usually has board on the inside only.
• Multiply by the number of layers the wall type calls for (a 2-layer each side wall is 4× the single-side area).

4. Openings: subtract the big ones only

Common practice is to ignore small openings (standard doors, small windows) — the cut-out usually becomes waste anyway. Subtract large openings like storefronts, big windows, and wide cased openings.

5. Divide by sheet size and add waste

A 4×8 sheet covers 32 sq ft; a 4×12 covers 48 sq ft. Divide total board area by sheet area and add 10–15% for waste (more for lots of small rooms and corners, less for long straight corridors).

6. Don't forget ceilings and soffits

Hard-lid ceilings come from the reflected ceiling plan: room area in sq ft, same sheet math. Soffits and bulkheads are easy to miss — check the RCP and sections.

Where estimates usually go wrong

• Wall types misread or a legend on a different sheet than expected.
• Board-to-deck walls counted at ceiling height.
• Second layers and both sides missed on rated or acoustic walls.

That's exactly the part ReadMyBlueprint automates: it reads the wall-type legend, matches each wall on the plan to its type, and shows you which walls it's sure about and which need your confirmation.

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Reference: Types of drywall: Type X, Type C, moisture resistant