Painting Calculators
Wall paint and wallpaper roll counts from room size, openings, coats, and pattern waste — plus a paint cost band.
3 calculators
Painting calculators here convert wall area, coats, and product coverage into litres or gallons — and wallpaper tools convert perimeter and pattern waste into roll counts. The goal is a shopping list you can defend at the trade counter, not a decorator’s full quote.
What this category covers
- Interior paint from room dimensions, openings, and coats.
- Paint cost when you want a materials band from coverage and price per tin.
- Wallpaper from walls, roll length/width, and pattern repeat waste.
Coverage is the number that lies most often
Tin labels quote coverage under ideal conditions. Rough plaster, deep colour changes, and cheap rollers burn through paint faster. If you are covering dark walls with light paint, plan an extra coat instead of shrinking the waste line to “save money.”
Measure height to the ceiling line you will actually paint. Vaulted ceilings and stair voids are easy to under-count from a floor plan alone.
Wallpaper specifics
Pattern repeats waste paper even when the wall area looks small. Straight-match and offset-match behave differently — enter the repeat from the roll label, not a guess from a phone photo. Openings (windows, doors) reduce paint area more cleanly than they reduce wallpaper; you still waste paper around reveals.
Exterior vs interior
These tools are tuned for interior room maths. Exterior masonry, render, and weather windows change coverage and product choice. If you are painting outside, treat the result as a starting quantity and confirm with the exterior product data sheet.
Related reading
Guides cover paint for a room, interior paint cost versus labour, and measuring a room for paint, flooring, and wallpaper in one pass. Use them when the calculator result looks fine but you still do not know how many tins to put in the basket.
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