Mathterial is a free set of construction calculators. How much concrete a slab takes, how many sheets of drywall a room needs, how many bundles of shingles a roof works out to. No sign-up, no paywall, and no email address required to see an answer.
The idea is to show the working
Most calculators on the internet give you a figure and stop. That is fine until the figure looks wrong, and then you have no way to find out whether the tool is mistaken or your assumption is. Every calculator here breaks its answer into the parts it was built from, so you can see which input is driving the result and check the one line you doubt.
It is also why the explanation sits on the same page as the tool rather than in a post somewhere else. The thing worth knowing about a concrete calculator is usually why two of them disagree, and that belongs next to the number. Nine times out of ten the answer is waste allowance.
Where the numbers come from
Coverage and yield figures come from the people who make the material. Bag yields follow the manufacturer’s printed figure rather than a rounded rule of thumb, because a 60 pound bag and an 80 pound bag do not fill the same hole. Spacing and span defaults follow common residential practice, and each page says which convention it is using rather than leaving you to work it out from the answer.
Where a figure varies by product, the calculator makes it an input instead of burying an average in the math. Tile size, board width and joist spacing are all things you can read off what you are actually buying, so the calculator asks rather than assumes.
What this site does not do
It does not ask you to create an account. It does not store what you type into a calculator. The figures you enter are used to work out an answer on screen and are not written to any record.
It does not replace a professional takeoff, and it is not structural advice. These are planning estimates, built carefully, and what you order is your call. Order slightly over rather than slightly under, and have anything load-bearing checked by somebody qualified to sign it off.
Mathterial is independent. It is not affiliated with any manufacturer, supplier or lumberyard, and nobody pays to be featured here.
If a number here looks wrong, please say so. Tell us which calculator, what you entered and what you expected, and we will check it against the source and publish a correction if the mistake is ours.