Plastering a wall or a whole room? Our free Plaster Calculator estimates the plaster volume, cement bags and sand you need from your wall measurements — with an allowance for wastage built in.
Dry volume is taken as 1.3 × wet volume; cement at 1,440 kg/m³, sand at 1.6 tonnes/m³. Everything runs in your browser; nothing is uploaded.
How to Use
- Enter the total length of all walls to be plastered, in metres.
- Enter the wall height and your planned plaster thickness in millimetres.
- Choose a cement-to-sand mix ratio (1:4 is standard for internal walls).
- Set a wastage allowance — 10% covers most site waste.
- Click Calculate to see the cement bags and sand required.
Key Features
- Wet plaster volume from your exact wall dimensions.
- Cement requirement in standard 50 kg bags.
- Sand requirement in cubic metres and tonnes.
- Adjustable mix ratio and wastage allowance.
- 100% private — all calculations happen in your browser.
FAQs
How much plaster do I need per square metre?
At 12 mm thick, one square metre needs about 0.012 m³ of wet plaster before wastage. The calculator above scales this to your full wall area automatically.
What cement-to-sand ratio should I use for plastering?
1:4 is the standard for internal wall plastering, while 1:3 gives a stronger mix for ceilings and external work. Richer mixes cost more but resist cracking better.
How thick should plaster be?
Around 12 mm for a single-coat finish on walls, or 10 mm base plus 3 mm finish for two-coat work. Thicker coats are more prone to shrinkage cracking.
How many cement bags per cubic metre of plaster?
Roughly 7.5 bags of 50 kg cement per cubic metre of wet 1:4 plaster, after allowing for dry volume. Your exact figure appears in the results above.
Is my project data sent anywhere?
No. The calculator runs entirely in your browser with JavaScript, so your measurements never leave your device.
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