Paint Calculator – Free Online Estimate Tool
Enter your wall dimensions and get an instant, accurate paint estimate. No guesswork, no over-buying — just the exact litres you need.
Free Paint Calculator
Paint Calculator
Enter your wall dimensions below
What Is a Paint Calculator and Why Do You Need One?
A paint calculator is a free online tool that removes the guesswork from your next painting project. Whether you're a professional painter estimating a job or a homeowner refreshing a room, knowing exactly how much paint to buy saves money, reduces waste, and prevents those frustrating mid-project trips back to the hardware store.
The calculation itself is simple: multiply your wall area (length × height) by the number of coats, then divide by your paint's coverage rate. But when you factor in multiple walls, surface type, doors, windows, and different coverage rates for different paints, it gets complex fast. That's what our calculator handles for you instantly.
How Paint Coverage Works
Coverage Rate (m²/L)
Every tin of paint lists a spreading rate, typically expressed as square metres per litre (m²/L). Standard interior paint covers 10–12 m²/L on smooth surfaces. Rougher surfaces like brick or textured render absorb more paint and reduce this to 5–8 m²/L.
Why Two Coats?
One coat rarely gives even, durable colour. Two coats is the industry standard for most interior and exterior surfaces. New surfaces or drastic colour changes — particularly going from dark to light — may need three coats. Always factor your number of coats into your calculation.
Surface Type Matters
Porous surfaces like new plaster, bare timber, or unprimed drywall absorb the first coat heavily. Always prime new surfaces to seal pores — this reduces the amount of topcoat you need and dramatically improves colour accuracy and durability.
Paint Coverage Quick Reference
| Surface | Coverage per Litre | Coats Needed | Notes |
|---|---|---|---|
| Smooth drywall | 10–12 m²/L | 2 | Prime if new |
| Previously painted wall | 10–12 m²/L | 2 | Clean and sand first |
| New plaster | 8–10 m²/L | 2–3 | Prime first |
| Masonry / brick | 5–8 m²/L | 2–3 | Use masonry primer |
| Timber / wood | 8–10 m²/L | 2–3 | Sand smooth |
| Exterior render | 6–9 m²/L | 2 | Use exterior grade paint |
| Metal | 12–14 m²/L | 2 | Use metal primer |
Tips to Get the Best Results
Always add 10% to your calculated quantity as a buffer for waste and touch-ups
Buy all tins from the same production batch to ensure perfectly consistent colour
Store leftover paint in sealed tins, stored upside-down in a cool, dry place
Apply paint in good lighting — it's easier to spot missed spots and thin areas
Use a quality primer on new or bare surfaces; it reduces topcoat quantity and improves adhesion
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