Guide
How to estimate paint quantity
Estimating how much paint a job needs, using the coverage rate stated on the product.
Answer
How much paint do I need?
Explanation
The calculation
Litres = net area ÷ coverage per litre per coat × number of coats. That is the whole arithmetic. What matters is that all three inputs are real.
Detail
What coverage rate should I enter?
The one stated on the product pack or its technical data sheet. It varies by product, and the same product covers differently on a smooth sealed wall than on porous new plaster.
Manufacturers usually quote a range. The lower end is the safer planning figure on an absorbent surface.
Detail
How many coats?
What the product system says. No coat count is universal — a strong colour change, a porous surface or a particular product may need more, and some jobs need fewer. The estimator asks you to enter it rather than assuming.
Detail
Allowance
Optional, and yours to decide. Allowance depends on surface, application method, container sizes, touch-up needs and project conditions. The estimator adds nothing unless you enter a figure.
Detail
Estimate each layer separately
Putty, primer and topcoat have different coverage rates and different coat counts. Running one figure across all of them produces a number that is wrong for each.
Questions
Also asked
Why does the shop figure differ from mine?
Usually coverage rate or coat count. Compare the actual figures rather than the totals — the difference is nearly always in one of the three inputs.
Should I round up to pack sizes?
That is worth doing at quotation, once the product and its available pack sizes are known. The estimator gives litres; pack sizes are a product question.
Next
Ready to plan it?
Measure the walls, estimate each layer and build a paint list to send as one structured requirement.