All Concrete Calculators

Which calculator for which job

Thirty-four calculators is more than anyone wants to read through, and several of them answer questions that sound identical until you have the numbers in front of you. This table is the short way in: find the job on the left, and the tool that answers it is in the middle.

If you would rather start with one tool, the free concrete calculator on the homepage handles slabs, footings, walls, tube forms, stairs and ramps.

If you do not have dimensions yet, start at how much concrete do I need, which works through sizing a slab, a footing and a post hole before any arithmetic. If you have the dimensions but not the thickness, slab thickness settles that first.

Calculators that sound alike

These six groups really do overlap. Underneath they run the same arithmetic, square feet times thickness in feet divided by 27, so two of them will never hand you different answers for the same inputs. What changes is what each one asks for, and what it adds on top.

Slab, floor, pad, or square footage

Use the slab calculator for a rectangle you can measure in feet. Use the floor calculator for an interior floor slab. Use the pad calculator when the pad is small and freestanding and the real question is how big to make it for the thing going on top. Use the square footage calculator when somebody has already handed you an area, say 420 square feet, and all you need is yards and bags. The sidewalk and driveway calculators are the same slab math with the joint spacing and the edge details those two jobs need.

The cost calculator, or a cost calculator for your job

The cost calculator prices a pour from the quantity up, so it suits anything. The job-specific ones start from the job instead and carry the charges that job attracts: slab cost, pad cost for a pour small enough that the load minimum dominates the bill, driveway cost, and steps cost. If the open question is concrete against another surface rather than how much concrete, the driveway cost calculator also prices asphalt, gravel and pavers beside it. Prices behind all of them are explained in how much concrete costs.

Footing, deck footing, sonotube, or fence post

The footing calculator handles continuous strip footings, pads and plain holes once you know the size. The deck footing calculator works the other way: give it the load and the soil and it returns the footing size the code table allows, then the concrete. The sonotube calculator is for a round pier formed in a cardboard tube, and it adds the pad underneath. The fence post calculator answers in bags rather than yards, because nobody orders a truck for a fence. How deep the hole goes is a separate question, answered in fence post depth.

Gravel, or crushed concrete

Two tools for the same geometry, because the two materials do not weigh the same. Use the gravel calculator for quarried stone, including dense-graded base, clean stone and pea gravel. Use the crushed concrete calculator for recycled concrete, which weighs less per cubic yard than quarried stone both loose and compacted. Both return tons, because aggregate is sold by weight.

Bags, a mix ratio, or a brand

The bag calculator counts bags of ready-to-mix concrete for a volume. The mix calculator is for mixing from raw materials and splits a batch into cement, sand and gravel at whatever ratio you give it. The Quikrete and Sakrete calculators work in the yields those two brands publish per product, which is what you want when the bag in your hand has a name on it.

Yardage, or weight

The yardage calculator is the plain one: volume in, cubic yards out, plus the yards you should actually order once waste and the truck minimum are in. The weight calculator answers a different question entirely, which comes up when you are loading a trailer, checking a slab against a floor or working out what a demolition will haul away. Background on both sits in the concrete yard guide.