Plaster/plasterboard estimator
Estimate both the plasterboard sheets and the skim plaster needed to board and finish a wall or ceiling.
Result
Plasterboard sheets
Skim plaster
How to use this calculator
- Measure the area to be boarded and skimmed.
- Enter how many skim coats you're applying (2 is standard).
- Read the sheets and plaster quantities.
Assumptions
- Standard 2400 × 1200mm plasterboard sheet (2.88m²).
- 1.2kg/m² per coat is a typical figure for finishing skim plaster; actual usage varies with wall flatness and plasterer technique.
Technical details: what the fields mean
- Wall/ceiling area
areaM2 - Total wall or ceiling area, in square metres.
- Skim coats
skimCoats - Number of finishing skim coats — 2 is standard practice.
- Waste allowance
wastePercent - Extra plasterboard for cuts around openings and board edges.
Methodology
Sheets = (area × (1 + waste%)) ÷ 2.88m² (a standard 2400 × 1200mm board). Skim plaster = area × 1.2kg/m² per coat × number of coats, a typical dry-plaster usage figure for a skim finish.
Worked example
12m² ceiling, 2 skim coats, 10% board waste
Inputs: areaM2=12, skimCoats=2, wastePercent=10
Result: 5 sheets, 28.8kg skim plaster
Practical guidance
- Buy a couple of spare plasterboard sheets — breakages during handling are common.
- Plaster is usually sold in 25kg bags; round the kg figure up to whole bags.
Common mistakes
- Forgetting that ceilings need the same waste allowance as walls for cut edges.
- Underestimating plaster on a rough or uneven substrate, which needs more material than a flat one.
FAQs
How many plasterboard sheets do I need for a 12m² ceiling?
5 standard 2400 × 1200mm sheets, allowing the default 10% waste.
How much skim plaster do I need per square metre?
Roughly 1.2kg per coat per square metre — this calculator assumes 2 coats by default.