Walls & Ceilings
Paint, wallpaper, drywall
Walls and ceilings are mostly straightforward area - until you account for what eats into it and what adds to it. Paint goes on in two coats, plus primer on bare or patched surfaces, so the real figure is roughly double the wall area. Wallpaper is sold by the roll but wasted by the pattern, and drywall comes in fixed sheets that rarely divide evenly into your walls. Getting each right starts with measuring the surface and knowing how the material is actually sold.
These calculators cover the whole wall build-out. Work out paint by coverage and coats, count drywall sheets for walls and ceiling, size a wallpaper order around its pattern repeat, and total the linear metres of baseboard and trim. R-value sits behind all of it - the insulation you choose before the drywall goes up. Once you have the quantities, the cost calculators turn them into a price with labour and materials.
Guides
Frequently asked questions
How much paint do I need for a room?
Measure the wall area (perimeter × height), subtract big openings like doors and windows, then multiply by the number of coats - usually two. A litre of wall paint covers roughly 10–12 m² per coat, a US gallon about 350 sq ft. Add primer if the surface is bare, patched, or a big colour change. The paint calculator handles the coats and coverage so you buy whole tins instead of guessing.
How many drywall sheets will I need?
Divide the total wall and ceiling area by the area of one sheet - a standard 1.2 × 2.4 m board covers about 2.9 m² (a 4×8 ft sheet is 32 sq ft) - then round up and add around 10% for cuts and waste. A few spare sheets are cheaper than a second trip to the store. The drywall calculator does the rounding and the waste allowance for you.
Does the wallpaper pattern change how many rolls I need?
Yes, and it can change it a lot. A plain or random-match paper wastes very little, but a large pattern repeat forces you to line up each drop, and the offcuts add up fast - a 50 cm repeat can waste 15–20% more than a plain wall. The wallpaper calculator factors the repeat into the roll count so you don't come up a roll short mid-wall.
What's the difference between the quantity and cost calculators?
The quantity calculators - paint, drywall, wallpaper, baseboard, board-foot - tell you how much material to buy. The cost calculators take those numbers and turn them into a price, adding labour and the extras a quote actually includes. Start with quantity, then feed it into cost so your budget matches what you'll really carry home.