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Render Quantity Calculator

Render volume = area × (scratch coat + top coat) × (1 + waste). 80 m² of render, 10 mm scratch coat plus 8 mm top coat with 10% waste, is 1.58 m³. In 1:1:6 cement-lime-sand that is 7.6 bags of cement, 158 kg of hydrated lime and 1.58 m³ of sand.

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Behind this panel: an example with the default sizes.

Inputs

Results update as you type.

Area
m²
Coats
mm
mm
Mix
Render 1:1:6 on 80 m²Render 1:1:6 on 80 m²wall scratch coat 10 mmtop coat 8 mmmyconstructioncalculator.comNot to scale
Diagram updates as you type.

Results

Check the working before you order.

Cement (50 kg bags)
7.6bags (379 kg)
Sand1.58 m³
Hydrated lime158 kg
Wet render (both coats)1.584 m³
Total thickness18 mm
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Working
  1. Wet render = 80.0 m² × (10 mm + 8 mm) × 1.10 = 1.584 m³
  2. Dry = × 1.33 = 2.107 m³, split 1:1:6: cement 0.263 m³ (7.58 bags), lime 0.263 m³ (loose lime ≈ 600 kg/m³ / 37 lb/ft³), sand 1.580 m³
Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.
Formulas


Site-mixed:  wet = area × (scratch + top) × (1 + waste)
             dry = wet × 1.33, split by cement : lime : sand
Premixed:    kg  = area × total thickness (mm) × kg/m²/mm × (1 + waste)


Worked example


80 m², 10 mm scratch + 8 mm top coat, 1:1:6, 10% waste:


    

  1. Wet render = 80 × 0.018 × 1.1 = 1.584 m³
    2. 

  2. Dry = 2.107 m³ → cement 0.263 m³ = 7.6 bags, lime 0.263 m³ ≈ 158 kg, sand 1.58 m³
    3. 



Premixed alternative: 80 × 18 × 1.6 × 1.1 = 2,534 kg ≈ 102 bags of 25 kg.


Common render mixes (cement : lime : sand)






Mix
Use






1 : ¼ : 3
Very exposed, dense backgrounds




1 : ½ : 4½
Exposed walls, strong backgrounds




1 : 1 : 6
General purpose




1 : 2 : 9
Soft or weak backgrounds






Frequently Asked Questions
How much render do I need per m²?
About 18–20 litres of wet render per m² for a two-coat finish 18–20 mm thick. For premixed renders, check the bag, often 1.4–1.8 kg per m² for each mm of thickness.
What mix is used for sand and cement render?
1:1:6 cement : lime : sand is a common general-purpose render; 1:½:4½ for exposed walls; 1:2:9 for soft or weak backgrounds. The top coat should not be stronger than the scratch coat.
How many bags of render do I need?
For premixed render, area × thickness (mm) × consumption (kg/m²/mm) ÷ bag size. 20 m² at 15 mm and 1.6 kg/m²/mm is 480 kg, about 20 bags of 25 kg.
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