The Ultimate Plasterboard & Drywall Calculator Guide
Whether you call it plasterboard (UK), drywall, or Sheetrock (US), boarding out a room is the first step in transforming a space. However, buying materials isn't just about the boards. You need to know exactly how many screws to drive, how much joint tape to run, and how much compound to mix. Underestimating means halting work to run to the store; overestimating eats into your profit margin.
Our Plasterboard Calculator is designed for both DIY enthusiasts and trade professionals. It handles the math for US sizes (4x8 sheets) and UK metric sizes (2400mm x 1200mm), automatically calculating waste allowances and finishing materials so you can order with confidence.
How to Measure Your Room
Before using the calculator, you need accurate surface dimensions.
- Walls: Measure the total length of all walls to be covered. Multiply by the ceiling height. If you are boarding a whole room, measure the perimeter and multiply by height. Tip: Don't subtract doors/windows unless they are very large. The off-cuts are useful for headers and fillers.
- Ceilings: Measure the Length and Width of the floor area. This gives you the ceiling square footage/meterage.
Understanding Board Sizes
The calculator adjusts based on your region:
🇺🇸 US Standards (Drywall)
- 4' x 8' (32 sq ft): The industry standard. Easy to handle, fits 16" stud spacing perfectly.
- 4' x 10' / 4' x 12': Used for high ceilings to avoid horizontal seams. Heavy to lift.
- Thickness: 1/2" is standard for walls. 5/8" is used for fire rating (garages) or ceilings to prevent sagging.
🇬🇧 UK Standards (Plasterboard)
- 2400mm x 1200mm (2.88m²): The standard "8x4" equivalent.
- 1800mm x 900mm: "Handy boards" designed for easy transport in cars and getting up tight staircases.
- Thickness: 12.5mm is standard. 9.5mm is lighter but less soundproof. 15mm is for sound/fire protection.
Finishing Materials Guide
Our calculator doesn't just count boards; it estimates the "fixings" and "finish":
| Material | Rule of Thumb | Notes |
|---|---|---|
| Drywall Screws | ~35 per board | Spaced every 12" (300mm) on studs. Use 32mm screws for single layer boarding. |
| Joint Tape | ~14ft (4.5m) per board | Covers tapered edges and butt joints. Paper tape is stronger; mesh tape is self-adhesive. |
| Joint Compound | ~1 lb (0.5 kg) per sq ft | Ready-mix bucket or powdered bag. Amount varies by finish level (Skim coat needs much more). |
Why Add a Waste Allowance?
You will rarely fit a board perfectly without cutting. When you cut a board to fit a corner, the off-cut might be too small to use elsewhere.
- Simple Rooms (Square): 5-10% waste is sufficient.
- Complex Rooms (Many windows/angles): 15-20% waste is safer.
Frequently Asked Questions (FAQ)
Should I board horizontally or vertically? â–¼
Vertical: Easier for DIY. Seams align with studs.
Horizontal: Preferred by pros for strength. Reduces linear footage of taping at eye level, but requires staggering butt joints.
What screw length do I need? â–¼
For standard 1/2" (12.5mm) board into wood studs, use 1 1/4" (32mm) coarse thread screws. For steel studs, use fine thread screws.
Do I need to stagger the joints? â–¼
Yes. Never have 4 corners meet at one point (a "cross" joint). Staggering joints strengthens the wall and makes hiding seams much easier during taping.
Ready to start boarding?
Scroll up and use the #1 Free Plasterboard Calculator now.