Paint & Walls Calculators
Wall projects start with one number: wall area = perimeter × height. A 12 × 12 ft room with 8 ft walls has 384 sq ft. Use it to size paint by spread rate, drywall by sheet area, wallpaper by strips and trim by linear feet with the tools below.
Paint Calculator
Gallons of wall paint for any room, after doors and windows.
Drywall Calculator
Sheets of 4×8, 4×10 or 4×12 drywall for walls and ceiling.
Wallpaper Calculator
Rolls of wallpaper by strips, with pattern repeat.
Crown Molding Calculator
Linear feet and 8, 12 or 16 ft sticks of crown molding.
Planning a wall project
Interior wall work usually happens in a fixed sequence: hang and tape gypsum board, prime, install trim, then roll the finish color or hang paper. Measuring once and reusing the numbers saves time. Write down the length of every wall, the ceiling height and how many doors and windows break up each surface, then feed the same figures into each tool. Keep receipts and unopened containers so you can return extras.
Which calculator do I need?
- Paint: you are repainting walls and want gallons after subtracting openings and choosing the number of coats.
- Drywall: you are finishing a basement, replacing damaged board or building a new room and need sheet and screw counts.
- Wallpaper: you are covering an accent or full room and the pattern repeat affects how many rolls you open.
- Crown molding: you are adding trim where the wall meets the ceiling and need sticks of 8, 12 or 16 ft.
Before you buy
Buy paint, compound and adhesive a day or two before you start so you can check colors in your own light. Store drywall flat and dry, and bring wallpaper rolls home together so the batch numbers match. Protect floors with canvas drop cloths rather than plastic, which gets slippery. If your home was built before 1978, test for lead before sanding old paint, and ventilate the room while primers and finishes cure.
Frequently asked questions
What order should I do wall work in?
Framing and insulation, then drywall, taping and sanding, primer, trim, and finally the finish coat.
Should I paint before or after installing trim?
Many DIYers prime and paint trim before installing it, then caulk and touch up, which reduces cutting in.
Can I wallpaper over fresh drywall?
Yes, after the joints are finished and the wall is sealed with a wallcovering primer.
Do these tools include openings?
The paint tool subtracts doors and windows; drywall and wallpaper leave them in as waste, as pros usually do.