ExactMaterials is built and maintained by Liviu Iulian Taune. It exists because every material calculator on the internet does the same two things — multiply length by width, add ten percent — and neither of those has anything to do with how material is actually cut and laid.
Why this exists
The idea came out of a floor that went wrong. A 14 by 12 bedroom, vinyl plank, ordered from an online calculator that returned 185 square feet. Eight boxes at 24 square feet each. It was two planks short on the last row, and by the time the shortage was obvious the store had moved to a different lot number. The replacement box was visibly lighter than the rest of the floor.
The mistake was not in the arithmetic. 168 square feet plus 10% really is 185. The mistake was that a 144 inch wall does not divide into 48 inch planks with the offcuts landing where the stagger rule allows them. Nobody had modelled the layout, because modelling the layout is the hard part and adding ten percent is the easy part.
So these tools place the pieces. Every calculator on this site draws your room at scale, lays the pattern you selected, marks each piece that has to be cut, and measures how much material the layout genuinely consumes. Then it compares that figure with the waste allowance a professional estimator would quote and shows you the higher of the two.
How the results are calculated
Everything runs in your browser. There is no server doing the sums, no account, no saved project, and your measurements are never transmitted anywhere. If you close the tab, the only trace is what your own browser chose to remember.
The engine works in inches internally, converting at the edges, so unit switching never introduces rounding drift. The layout engine places pieces by pattern — grid, brick offset, diagonal, herringbone, chevron, basketweave and random plank stagger — then clips each piece against the room outline to decide whether it is a full piece or a cut.
It also models what an installer does with the offcuts. A perimeter cut that leaves a usable piece goes onto the scrap pile and is used again when a cut of that size comes up; anything under a quarter of the piece is treated as waste. That single behaviour is why the numbers here are usually lower than a naive "count every cut as a whole tile" calculation and higher than the optimistic 5% that gets quoted in the aisle.
Purchase quantities always round up, because boxes, bags and sticks are not sold in fractions. Areas are shown to one decimal, money to two, percentages to one.
Where the prices come from
Every price on this site is a US national average for mid-range product, collected from published retail pricing at national home centres and flooring retailers. They are starting points, and every one of them is editable in the calculator — if your quote says $3.10 a square foot, type that in and the totals follow.
The reference set was last reviewed on 2026-09-01. It is reviewed every three months. Material prices in this category move several percent a quarter and stale prices are worse than no prices at all, so if that date is more than four months old, treat the cost figures as indicative and the quantities as sound.
Coverage figures — 350 square feet per gallon of paint, 95 square feet per bag of thinset, 0.7 gallons of joint compound per 100 square feet of board — come from manufacturer technical data sheets. Where sources disagree, the more conservative figure is used, because running short mid-job costs more than one spare bag.
What this site is not
It is not a substitute for a contractor, a structural engineer or your local building code. It will tell you how many sheets of drywall a room takes; it will not tell you whether that wall needs fire-rated board, and the answer to that question is in your local code, not here.
It does not sell anything. There are no affiliate links, no sponsored products, no lead-generation forms selling your project to three contractors. Nothing is ranked or recommended because someone paid for it.
How it is paid for
This site is free and is funded entirely by display advertising. The ads are served by Google AdSense, they are clearly labelled, and there are never more than three of them on a page. None of them are placed inside the calculator, next to a button, or anywhere they could be mistaken for part of the tool.
No one pays for placement in the content, and the ads have no influence on what the calculators recommend or what the guides say. If a paid arrangement ever exists, it will be labelled on the page where it appears.
Corrections
If a number here is wrong, tell me. Coverage figures change when manufacturers reformulate products, stock sizes vary by region, and code requirements are revised. Corrections that come with a source get made quickly and the guide's updated date changes to reflect it. Write to [email protected] or use the contact form.