Dot and Dab Calculator — Adhesive & Plasterboard Estimator

Our dot and dab calculator works out both the adhesive and plasterboard quantities for your project. We calculate the total wall area and divide by the coverage rate for your chosen adhesive, plus the number of plasterboard sheets needed.

The formula

Adhesive bags = Total area ÷ Coverage per bag × Wastage factor

Plasterboard sheets = Total area ÷ Sheet area × Wastage factor

Coverage rates

• Gyproc Dri-Wall adhesive: ~5.76 m² per 25kg bag (British Gypsum states 2 standard 2400 × 1200mm boards per bag under normal use)
• Knauf Perlfix: ~4.6 m² per 25kg bag (Knauf plasterboard adhesive, dot & dab)
• Generic adhesive: ~5 m² per 25kg bag (conservative blended default)

These are coverage rates for a flat, plumb masonry wall. Uneven or out-of-plumb backgrounds use more adhesive — increase the wastage allowance to suit.

Application method

The standard dot and dab method uses dabs at 600mm horizontal centres with three columns per board width. A continuous ribbon of adhesive runs along the top (ceiling line) and bottom (floor line) of each board. This is the method recommended by British Gypsum for their Gyproc plasterboard range.