About HowMuch

Why this site exists

Search for the concrete in a small slab and you get several different answers. Most of the calculators returned show no working at all, and the failure modes repeat: bag counts rounded down rather than up — the one direction that guarantees a second trip to the store mid-pour, with concrete already going off in the mixer — no waste allowance anywhere on the page, and coverage figures that no manufacturer actually prints.

That is the normal state of this corner of the web: pages built to hold ads, with the arithmetic as an afterthought. It is a solvable problem, because the correct numbers are already public. Manufacturers print bag yields on the bag. Trade associations publish coverage rates. The waste factors estimators use are documented. The work nobody was doing is the dull part — looking each one up, and saying on the page where it came from.

What we do differently

Four rules, applied to every page:

• Every yield figure is a published figure, and the page names it. If a calculator uses "0.6 cu ft per 80 lb bag", that number appears in the text with where it comes from, so you can check it against the bag in your hand instead of trusting us. If we cannot source a figure, we do not ship the calculator — we would rather have a gap than a plausible invention.
• Waste is a visible input, not a hidden multiplier. Where the trade normally adds an allowance, there is a field for it, pre-filled with the conventional figure and explained. You can see it, and you can change it, which matters because a 5% allowance on tile and a 15% allowance on a diagonal layout are different jobs.
• Counts round up, in the unit you actually buy. Bags, sheets, boards and rolls come in whole numbers. 11.2 bags means 12 bags. Volumes are given in the unit a supplier quotes — cubic yards for ready-mix, not cubic feet.
• The page says what the number leaves out. A slab calculator that never mentions the gravel base or the rebar has told you half of what you need to buy. Each page has a section on what is not included and where the estimate typically goes wrong on a real site.

How a calculator gets written

Each one is a single small program with the formula, the input fields, the explanation and the sources in one place. Building one goes:

1. Establish the geometry from first principles — volume, area or linear run — and keep it in one canonical unit so no conversion happens inside the formula. Unit conversion is where these things quietly break.
2. Find the yield or coverage figure in a manufacturer's data sheet or a trade association's published guidance, and write it into the page text with its origin. Not a figure copied from another calculator.
3. Add the allowance the trade actually uses, and say why it is that size.
4. Test the result against a worked example from an independent source — a supplier's own chart, a published take-off — and against the arithmetic by hand. If they disagree, we find out why before publishing.
5. Write the explanation for someone standing in a store aisle with their phone: what to buy, how many, what goes wrong.

Every page carries a "last reviewed" date at the bottom. That is not a decoration — it is when a person last checked the figures against current product data. Manufacturers change formulations and bag sizes, and a calculator that was right in 2024 can drift.

What we are not

We are not engineers and we do not pretend to be. Nothing here designs a structure. Quantities are one thing; whether a slab is thick enough for what you will park on it, how it is reinforced, how deep a footing goes below frost — those belong to a licensed engineer and your local building department. Where a calculation touches that boundary, the page says so rather than guessing. The terms of use spell out where our responsibility ends.

We are also not a shop. There is nothing to buy here, no lead form, and no affiliate link dressed up as a recommendation. The site is paid for by display advertising, which means the only thing we owe you is a page worth the visit.

Corrections

If a number on this site does not match what you needed on the job, we want to hear about it — that feedback is worth more than any amount of internal review, because you were there. Email tsuyoshi.gt@gmail.com with the inputs you used and the quantity you actually used up. Corrections go to the front of the queue, ahead of new calculators, and the reviewed date on the page moves when one lands.

Who runs it

Eioto Studio is a small independent studio that builds and maintains its own web tools. HowMuch is written in-house — there is no content pipeline and no outsourced writing. If you email, you reach the people who made the page you are reading.

Contact: tsuyoshi.gt@gmail.com · more ways to get in touch