How it’s calculated
Net lining area = wall faces + ceilings − openings. Multiply by board layers and 1 + waste/100, divide by sheet area, then round up. Compound uses finished face area × your combined kg/m² allowance × waste factor, rounded up to whole packs. Stopping labour uses finished face area once, not every hidden board layer. GIB’s official stopping guidance determines suitable products and joint systems; the 0.5 kg/m² default is an editable budgeting assumption, not a manufacturer coverage claim.
Worked example
100 m² walls plus 40 m² ceilings minus 10 m² openings gives 130 m². One layer of 2.4 × 1.2 m sheets with 10% waste needs 50 boards. A 0.5 kg/m² combined compound allowance needs 71.5 kg, rounded to four 20 kg packs.
Before you use the result
Measure both sides of partitions separately. Area-based sheet counts cannot optimize cuts or joints; check the sheet layout before ordering. Compound types, coat counts, joint density and finish level vary. This is joint stopping, not full-surface skim coating. Replace the allowance with product-specific coverage or separately price base and topping products. Costs exclude board fixing labour, screws, adhesive, tape, trims, delivery, access, painting and tax unless included in your prices. Rated fire, acoustic and bracing systems need their specified board type, layers and fixing schedule.
Frequently asked questions
Does a second layer double stopping?
No. Board quantities multiply by layers; compound and stopping labour model the exposed face only. Hidden-layer joint treatment required by a tested system must be added separately.
Is waste an exact cutting plan?
No. Waste is a planning allowance. Board orientation, room geometry and available stock lengths need a layout check.