Work out exactly what to order
Material quantity calculators for renovation work — tile, paint, flooring, drywall and concrete. Built around the numbers that actually decide the answer: laying pattern, coverage rate, pack size and finish level, not a flat 10% on everything.
Tile calculator
Tiles, boxes, adhesive and grout — with waste set by your laying pattern and grout derived from the tile geometry.
Paint calculator
Litres and the best combination of tin sizes, with the first coat priced separately because porous surfaces drink it.
Flooring calculator
Packs, underlay and trim — plus the last-row check that tells you whether to rip the first row before you start.
Drywall calculator
Sheets, screws, tape and jointing compound — with the compound driven by the finish level you are aiming for.
Concrete calculator
Volume for slabs, footings and post holes, converted into bags or a ready-mix order — and which one you should buy.
Reference tables
The waste factors, coverage rates and consumption figures every calculator here uses, with the reasoning behind each one.
Why these give different answers
Most material calculators do the same two things: multiply length by width, then add 10%. That is a reasonable approximation for a plain grid in a square room, and it is wrong almost everywhere else — sometimes by enough to stop a job.
Waste depends on the pattern, not the room
Material is wasted at cuts. A herringbone floor makes a continuous run of compound cuts around the entire perimeter and cannot absorb an odd offcut anywhere, so it needs roughly 18–20% extra. A straight run along the long wall recycles each row's offcut into the start of the next row and needs about 8%. Ordering both at 10% means over-buying one and running short on the other — and running short means a second delivery in a different batch, which on tile is visible forever. The full set of figures is in the waste factor table.
The first coat is not the same as the second
New plaster and new plasterboard absorb paint. The first coat covers about three-quarters of what the tin claims; later coats cover what it claims. Calculators that multiply area by coats and divide by the tin figure understate a room by roughly 20%, which is most of a tin. See the coverage rates.
You buy packs, tins and bags — not square metres
Knowing you need 7.3 litres of paint or 41.6 m² of flooring is only half an answer. These calculators round to what the merchant will actually sell you, work out which combination of tin sizes wastes least, and tell you how much you will have left over for repairs.
The numbers are derived, and the method is published
Grout quantity, for instance, is not looked up in a chart — it comes out of the tile geometry, so it stays correct for tile sizes no chart covers. Every calculator page shows its formulas and states its assumptions, so you can check the arithmetic rather than trusting it. Where a figure is our own working estimate rather than a manufacturer's published value, we say so.
Everything here is metric and imperial. Use the switch in the header. Your inputs convert with it rather than being reinterpreted, so nothing changes size when you flip between them.
Reference data
- Waste factor table — every pattern and material, with the reasoning and three worked examples
- Paint coverage rates — by surface, with first-coat absorption factors and a coats-needed table
- Adhesive and grout coverage — trowel notch consumption, and the formula that derives grout from tile size
All figures are planning estimates. Manufacturer data sheets and local building regulations take precedence over anything on this site. More about how this is put together.