About ConcreteCalculus

ConcreteCalculus works out how much concrete to buy for a project: cubic yards or cubic meters for a ready-mix order, how many bags of each size, what those bags weigh, how many truckloads you need, and, if you enter your own prices, whether bags or a truck costs less. It covers 15 shapes, from simple slabs and fence posts to bell footings, stairs with a landing, and walls with door and window openings, and you can combine several of them into one project.

Who runs it

ConcreteCalculus is an independent website run by one developer based in India. It isn't owned by, sponsored by or affiliated with any cement maker, bag brand, ready-mix supplier or hardware store, and no company pays to have its products listed or recommended.

Who it's for

The site is built for homeowners, DIYers and small contractors who need a reliable quantity before they buy: someone pouring a patio, setting fence posts, forming a shed base or pricing a small job. US units are the default, and every calculator switches to metric for readers in the UK, Europe, Australia, India and elsewhere.

It's designed to be used outdoors on a phone: large text and buttons, light and dark themes, a printable shopping list, and it keeps working without a signal once you've opened it.

How we keep the numbers right

• Every figure has a source. Bag yields come from the manufacturers' own data sheets (17 products at the moment). Concrete density and truck sizes come from the National Ready Mixed Concrete Association, and minimum slab thickness from the International Residential Code. Each page lists its sources and the date we checked them.
• No invented data. If we can't find a published figure, we don't guess. That's why the calculator never shows a sample price and never labels a thickness as right for a particular use without a source.
• The math is open. Under every result, "Show the math" lists each step with its units, from the first conversion to the final bag count. The full method is on How we calculate.
• It's tested. One calculation engine powers every page, and it's checked by automated tests on every update, including hand-worked examples for every shape and comparisons with figures that manufacturers publish themselves.
• It rounds the safe way. Orders and bag counts are always rounded up, and the weight of poured concrete uses the upper end of the published range, so estimates err toward having enough.

When something's wrong

If you find a mistake, a broken link or an outdated figure, please tell us. We check every report, correct the page if we got it wrong, and update the "Last updated" date at the bottom. Sources are reviewed regularly, because manufacturers change bag sizes and data sheets from time to time.

What the site won't do

ConcreteCalculus estimates material quantities. It doesn't design footings, slabs or walls for loads, check reinforcement, or replace your plans, your local building code or a professional's advice. Ground conditions, form work and waste vary from job to job, so always confirm quantities with your supplier before you order. The full terms are in our terms of use.

Your data

There are no accounts. The dimensions and prices you type stay in your browser, and saved projects are stored on your device only. Our privacy policy explains exactly what is stored and collected.

How the site is funded

The calculators are free and will stay free. To cover hosting and development, the site may show advertising. Ads never appear inside the calculator, and they never change a result, a source or a recommendation.

Get in touch

Questions, corrections or ideas for a new calculator are welcome at concretecalculuscontact@gmail.com. We reply within one day.