Buying the right amount of paint is one of those everyday problems that's easy to get wrong by 30-50%.
About this calculator
Buying the right amount of paint is one of those everyday problems that's easy to get wrong by 30-50%. Run short and you face a colour-batch mismatch when buying a top-up. Buy too much and you waste money plus litres of paint that goes to landfill. The good news: a few measurements and the right formula give you a precise estimate that beats any 'just buy 5 litres extra' guess.
This calculator follows the standard estimation method recommended by Asian Paints, Berger, Nerolac and most paint manufacturers. Wall area is the perimeter times the height. From that, subtract doors (~1.8 m² each for a standard 7×3 ft door) and windows (~1.6 m² each for a standard 4×4 ft window). Optionally add the ceiling (length × width). Multiply the resulting paintable area by the number of coats, divide by your paint's coverage rate (printed on the can, usually 90-130 m² per litre for emulsions and 80-110 for enamels), and add a 10-15% wastage buffer.
The wastage buffer is critical and often skipped. Real walls have texture, corners, brush losses, drips, the bottom of the can you can't reach, and the inevitable second-touch-up. New walls need an extra primer coat (apply the calculator separately for primer). Texture-finished walls need 20-30% more paint. Light-to-dark colour changes typically need 3 coats and a colour-blocking primer. The cost field gives a rough budget; multiply by 2-3 for a full painting project once you include primer, brushes, rollers, masking tape, ladders and labour. Combine with the [[area]] calculator for irregular shapes, the [[cylinder]] calculator for round columns and the [[paint]] section above when planning multiple rooms.
Common uses
- Estimating paint quantity and budget before a renovation
- Comparing emulsion vs enamel vs distemper based on coverage and price
- Sizing primer and putty quantities (use coverage of those products)
- Planning DIY painting projects -- single room or whole house
- Quoting jobs as a contractor or interior designer
Frequently asked questions
What coverage rate should I use?
Check the paint can specification. Premium acrylic emulsions cover 100-130 m² per litre per coat. Standard emulsions are 80-110. Distemper covers 60-80. Enamels and primers are typically 80-100. Texture and rough surfaces reduce coverage by 20-40%.
How many coats do I really need?
Two coats is the practical minimum for a colour change or new wall. Three coats are needed for very light colours over dark, or for a deep, even sheen on enamels. Single coat works only for refresh of the same colour on smooth walls.
Should I include the ceiling?
Yes if you
What about primer?
Primer is mandatory for new plaster, putty repairs and major colour changes. Calculate primer separately using its own coverage (usually 80-100 m² per litre) -- one coat is usually enough.
Why is my actual usage different from the estimate?
Real-world variables: wall texture (rough = 20-40% more paint), application method (roller saves vs brush, sprayer is most efficient), painter skill, drying conditions, and how dark the existing colour is. The 10-15% wastage buffer covers most of this; raise it to 20-25% for textured or rough walls.