50 Specialist Calculators
Instant Results - No Sign-Up
Free to Use
Professional tools for serious builders
Plastering a wall
Home Calculators Render & Plaster Calculator

Render & Plaster Calculator

Calculate bags of plaster or render needed for any coat system - internal plaster, external render, skim, monocouche and more.

Render & Plaster Calculator

Add each surface, choose your system, and get a full bag count per coat

Metric (m) Imperial (ft / in)

Surfaces

Coat settings - adjust thickness and coverage to match your product
10%
Allows for mixing losses, uneven backgrounds and overshoot on textured finishes

Job Costing

Enter costs in your local currency - the calculator works with any currency as long as values are consistent.

Results

Total Surface Area
-
m² (after deductions)
Number of Coats
-
-
Total Bags
-
inc. waste
Total Volume
-
m³ (all coats combined)

Bags per Coat

Coat Thickness Coverage / 25kg bag Net Bags Waste To Order

System Guide

  • Skim only - Over sound plasterboard or existing plaster. 2-3mm, very fast application.
  • Bonding + skim - Most common internal system. Bonding grips difficult backgrounds; skim gives smooth finish.
  • Hardwall + skim - Dense, impact-resistant base for commercial or high-traffic areas.
  • Sand & cement - Durable external render, needs weathering or painting. Often pebble-dashed.
  • Monocouche - Pre-coloured single-coat external render. No painting needed. Common in new build.
  • Silicone render - Flexible, self-cleaning finish coat. Applied over a base coat. Premium product.
  • Lime render - For older solid-wall buildings, heritage work and eco builds. Breathable and flexible.

Coverage Rates

Coverage rates are approximate averages. Always check the product data sheet for your specific brand - coverage varies significantly between manufacturers.

  • Skim (2mm) - ~10 m² per 25kg bag
  • Bonding/Hardwall (11mm) - ~2.8 m² per 25kg bag
  • One coat plaster (12mm) - ~2.5 m² per 25kg bag
  • Sand & cement (12mm) - ~1.5 m² per 25kg bag
  • Monocouche (15mm) - ~1.8 m² per 25kg bag
  • Lime render (10mm) - ~1.2-1.5 m² per 25kg bag

Tips

Always apply PVA bonding agent or specialist primer to the background before plastering. The right primer improves adhesion and reduces suction, which can cause the plaster to dry too quickly and crack.

For external render on solid walls, allow at least 24 hours between coats to avoid the base coat pulling moisture from the top coat.

On uneven backgrounds, increase your waste factor to 15-20% - more material is needed to build out hollows and level the surface.

Related Calculators