Everyday Life & DIY Calculators
Most home projects fail at the store, not at the job. You either guess high and carry back three unopened bags, or guess low and lose a Saturday to a second trip. The estimators here use the coverage rates printed on the product and the waste allowances trades actually plan for, then tell you which assumptions they made, so the figure you take to the counter is one you can adjust rather than a number you have to trust blindly.
Decorating a room: the Paint Calculator works from wall area minus doors and windows, and the Tile Calculator and Wallpaper Calculator add the overage that cuts and pattern repeats eat. Outside, the Concrete Calculator, Gravel Calculator and Mulch Calculator convert an area and a depth into cubic yards or bags. Beyond the house there is the Fuel Cost Calculator for a road trip, the TV Size Calculator for viewing distance, and the Recipe Scaler when dinner suddenly has to feed eight.
Estimates depend on conditions the calculator cannot see. Paint coverage drops sharply on bare plaster or a dark color being covered, and two coats are normal rather than exceptional. Material quantities assume a level surface and consistent depth, which yards and old houses rarely provide. Check whether results are in US or imperial units before ordering, since bag sizes and board dimensions differ on each side of the Atlantic. For structural work, follow local building regulations and confirm loads with a qualified builder.
63 free tools — all run entirely in your browser.
Frequently asked questions
How much paint do I need for a room?
Measure each wall, add the areas together, subtract doors and windows, then enter the total in the Paint Calculator along with the number of coats. It divides by the coverage rate on the tin, typically around 350 square feet per gallon or 12 square meters per liter. Bare or previously dark walls absorb more, so round up rather than down.
How much extra material should I order for waste?
Ten percent is the usual allowance for straight tile or flooring layouts, rising to about fifteen percent for diagonal patterns, busy room shapes or anything with a repeat to match. Bagged materials like concrete and gravel settle and compact, so a little spare is cheaper than a second trip. Keep offcuts from the same batch for future repairs, since colors vary between production runs.
Are these estimates accurate enough to buy materials from?
They are as good as your measurements, which is why the tools show the working. Treat the output as a shopping figure, not a quote: real rooms have alcoves, uneven floors and awkward corners that change the count. For a large or structural job, have a contractor confirm quantities before you order a delivery you cannot return.