Concrete Calculator

You've measured the patio twice. Ten feet by ten, four inches thick. Now you're facing a pallet of 80 lb bags and trying to do cubic feet in your head while someone waits behind you with a cart. Buy too few and the pour stops halfway. Buy too many and you're hauling bags back.

Concrete Calculator does that sum for you. The page opens on that same 10 ft by 10 ft by 4 in slab and answers in cubic yards and in whole bags, rounded up. With the default reserve it comes to 62 bags of 80 lb mix. Swap in your own measurements and the numbers update as you type.

Real projects are rarely one neat rectangle, so the calculator covers six shapes: slab, wall, round, tube, stairs and ramp. A project can hold several areas, and each measurement can use its own unit, so feet for the length and inches for the thickness need no converting. A 3D preview you can rotate helps confirm the shape on screen is the one in your yard.

The reserve is easy to forget, so the calculator puts it up front. It starts with a visible 10% and lets you pick 0%, 5%, 10% or your own figure, then shows the net volume and the total side by side. Bag counts come from preset yields for QUIKRETE Concrete Mix No. 1101 in five bag sizes, or from a custom yield you enter. The tool is independent and isn't affiliated with QUIKRETE.

If you add a price per bag or per yard, you get a material cost in one of five currencies. Delivery, labor, pumping and tax aren't included. Underneath, a worked breakdown follows your inputs through every step, which is a nice touch when you want to check the math before spending money.

The tool is free and needs no account. According to the privacy policy, updated October 3, 2026, your inputs live in the page's memory and aren't saved in cookies or browser storage, and the site runs no analytics scripts or advertising pixels. Sharing works by packing the project into the link itself, so anyone who has the full link can read the measurements and prices in it.

The about page says the tool is developed and maintained under the pen name Evan Brooks, based in New York, and describes it as a planning tool, not a structural engineering service. Unit conversions follow NIST factors. Treat the result as an order estimate and ask a professional about anything load-bearing.

Next time a pour is on the weekend list, run the numbers here before you leave for the store.