Material take-offs and code checks for the jobs that normally send you to twenty browser tabs, stairs, air conditioning, fencing, sod, tile, epoxy floors and decking. Every calculator uses the published industry figure or building-code limit behind it, not a guessed rule of thumb, and every page shows where the number comes from.
A unit converter answers "what is 12 feet in metres". These calculators answer "how many boards do I buy", and that question has no single correct answer, it depends on a code limit, a manufacturer's coverage figure, or a trade convention. So every page here names its source.
Three kinds of number appear on this site. Code limits come from the International Residential Code, for example the 7¾ inch maximum riser and 10 inch minimum tread that govern a staircase. Sizing rules come from a published standard, the US Department of Energy's 20 BTU per square foot cooling baseline, for instance. Material coverage comes from how the product is actually sold, a sod pallet covers 400 to 500 square feet, a tile box covers whatever the manufacturer packs into it.
Where a trade genuinely disagrees with itself, the page says so instead of picking a number and hiding the argument. Stair comfort rules are a good example: the 17–18 inch riser-plus-tread rule and the 2R+T rule are conventions, not code, and this site labels them that way.
Most estimating errors are measurement errors, not arithmetic errors. Measure the finished surface, not the rough framing. Use the actual width of lumber, not the nominal name, a 5/4×6 deck board is 5.5 inches wide, not 6, and a 2×4 is 3.5 inches. And when a calculator tells you it rounded up, leave it rounded up: the difference between the exact figure and the next whole board is a second trip to the supplier.
These calculators are estimating tools. Confirm quantities against your own measurements and your local building department before you buy or cut.