BuildCalcs Render Calculator
Estimate render area, volume and bags from the wall size, openings, application thickness and product bag weight.
Render quantity calculation
BuildCalcs subtracts the entered openings from the wall area, multiplies the remaining area by the render thickness and converts that wet volume into an approximate material weight.
One coat or multiple coats?
Enter the combined finished thickness you expect to apply. Base coats and finish coats can use different products and yields, so calculate them separately if necessary.
Frequently asked questions
Why might the bag count differ from the bag label?
Real product yield depends on formulation, aggregate size, water addition, substrate texture and wastage. Use the label's stated coverage when buying a specific product.
Can I use this for internal plaster?
The geometry is similar, but material density and product coverage differ. Use the plaster product's own coverage figures rather than assuming render values.
Related calculators
From wall area to render bags
The calculator deducts the entered openings from the wall area, multiplies the remaining area by the application thickness and converts that volume to a mass using the planning density. It then divides the mass by bag weight and adds the selected allowance. Because render products vary greatly, the most reliable cross-check is the manufacturer's stated coverage at the intended thickness.
Thickness changes consumption directly
A 15 mm coat uses 50% more material than a 10 mm coat over the same wall area. Uneven masonry, dubbing-out and multiple-coat systems can increase consumption further. If the wall requires a base coat and a finish coat made from different products, calculate or verify each product separately rather than treating them as one uniform layer.
Use product data where available
The adjustable density is intended for planning where only mass and thickness information are available; it is not a substitute for a tested coverage figure. Check bag yield, permitted coat thickness, substrate preparation and reinforcement requirements on the system data sheet. Beads, mesh, primers and other accessories are outside this material estimate.