Paint & Wallpaper Quantity Calculator
Enter your room dimensions to estimate how much paint or wallpaper to buy.
Total wall area to cover
418 sq ft
Paint needed
3 gallons
Estimated cost: $75–$180 (rough estimate, varies by region and product).
Wallpaper needed
9 rolls
Estimated cost: $270–$720 (rough estimate, varies by region and product).
How to use this tool
- Measure length, width and ceiling height in feet — these give the tool the total wall area to cover.
- Enter how many doors and windows the room has; the tool subtracts a standard allowance for each so you don't overbuy.
- Set the number of coats you're planning — most colors need 2 coats, but a big color change (dark over light, or vice versa) often needs a 3rd.
- Compare the gallon or roll count against your local store's pricing to firm up the rough cost estimate.
Tips for better results
Round up, always
Paint and wallpaper are sold in fixed sizes, so the tool already rounds up to whole gallons and rolls — buy that amount, not less, to avoid a mismatched batch later.
Dark or saturated colors often need an extra coat
Deep reds, blues and true black frequently need a 3rd coat regardless of what the can says — factor that in before you buy.
Patterned wallpaper needs extra for matching
If your wallpaper has a repeating pattern, add 10–15% more rolls than this estimate to account for pattern-matching waste at the seams.