Find net area
Floor length × width, or wall length × height with openings deducted.
Free South African screed and plaster calculator
Screed & plaster
calculator.
Convert floor or wall dimensions and finished thickness into wet mortar volume, 50 kg cement bags, building sand and an indicative material cost.
Calculate materials ↓mmArea × thickness
01Floor screed
volume
volume
02Wall plaster
area
area
03Adjustable
mix ratio
mix ratio
04Cement, sand
and cost
and cost
01
Mortar quantities
Area × finished thickness
Use the average finished thickness. Uneven substrates can consume substantially more material than the nominal specification.
02
The method
From finished layer to loose materials
The dry-material conversion matters because loose cement and sand occupy more volume before water and compaction.
Apply thickness
Finished millimetres are converted to metres to calculate wet mortar volume.
Convert dry volume
A planning factor accounts for voids and consolidation in the loose ingredients.
Split the mix
The selected cement-to-sand ratio converts dry volume into bags and sand.
Preparation matters
Thickness cannot fix a weak substrate.
Bond, cracks, movement, falls, moisture and curing must be addressed before screed or plaster is applied.
Check damp symptoms →Good to know
Screed and plaster FAQs
How do I calculate screed volume?+
Multiply floor length × width × average finished thickness in metres. A 5 m × 4 m floor at 30 mm is 0.60 m³ before waste.
How thick should plaster be?+
Thickness depends on the substrate, system and specification. This tool estimates materials from a thickness you provide; it does not prescribe the correct build-up.
Why is dry volume higher than wet volume?+
Loose sand and cement contain voids and consolidate when mixed and placed. The dry-volume factor provides a planning allowance for that change.
Does the calculator include waterproofing or bonding liquid?+
No. Primers, bonding agents, fibres, waterproofing admixtures, membranes and proprietary screed products must be allowed for separately according to their data sheets.