About & methodology

Wallpaper Calculator is a free tool that estimates how many rolls a job needs, and what they cost, from your wall size and roll dimensions. No sign-up; the math runs in your browser. It uses the strip method professional decorators use — not a rough area ÷ roll-coverage guess — so it accounts for the waste a pattern repeat creates.

How it works

• Wall run = room perimeter (2 × [length + width]), or enter the total wall width directly.
• Doorways are subtracted from the wall run (you don't paper them); windows are not, because strips still run past them and the offcuts cover above and below.
• Strips needed = wall run ÷ roll width, rounded up.
• The drop = wall height + a small trim allowance, rounded up to a whole pattern repeat for a straight match (plus half a repeat for a drop/offset match).
• Strips per roll = roll length ÷ the drop, rounded down.
• Rolls = strips needed ÷ strips per roll, rounded up. Cost = rolls × your price per roll.

Important

These are planning estimates. Complex walls, half-drop patterns, and lots of windows or angles raise waste. Buy one extra roll and make sure every roll shares the same batch or lot number so the color matches. Keep the leftover — wallpaper lines are discontinued often.