Concrete Calculator
Results update as you type, there is no submit button.
Switch between the slab tab and the column/footing tab depending on what you're pouring, check the waste-factor box to add a 10% margin, and this calculator returns cubic feet, cubic yards and the number of 60 lb bags the pour would take if you mixed it by hand.
Ready-Mix vs. Bagged: The Threshold
Because a 60 lb bag yields about 0.45 ft³, it takes roughly 2.2 bags per cubic foot and about 60 bags to make a single cubic yard, the same figures already established on this site's homepage. Sixty bags is usually the point where a project tips from bagged mix to a ready-mix delivery: mixing that many by hand is a full day of work, and the concrete has to go in continuously to avoid cold joints between batches. If you're trying to decide which side of that line your pour falls on, the cubic-yard converter converts this page's cubic-feet result straight to the unit ready-mix trucks actually price by.
Slabs
A slab is a flat, wide cuboid, so the standard length × width × thickness formula applies directly, with thickness standing in for height. A 12 ft × 10 ft patio poured 4 inches thick works out to 40 ft³, just under 1.5 cubic yards. The same slab poured 5 inches thick instead jumps to 50 ft³, a useful reminder of how sensitive volume is to a thickness that often looks like a minor spec change on paper.
Typical thickness varies by what the slab carries. A garden path or stepping-stone slab can get away with as little as 2 inches; a patio or shed floor is usually poured 4 inches; a driveway that carries vehicle weight is typically 5–6 inches, and often thicker still where it meets the street apron. Always check local code for anything a vehicle will drive on, since minimum thickness and reinforcement requirements for driveways are one of the more commonly enforced parts of a residential building code.
Columns and Footings
Footings and columns are long, narrow volumes calculated the same way as any other cuboid or cylinder, trench length × width × pour depth for a rectangular footing, or the cylinder volume formula for a round one poured in a sonotube or auger-dug hole. Where a rectangular footing turns a corner, treat each straight run as its own section and add the volumes together rather than measuring the full perimeter as one length, which would double-count the corner. For a purely round pour, the dedicated cylinder volume calculator handles the radius-and-height math directly.
Fill Dirt and Excavation Before the Pour
Any footing or slab that requires digging first adds a second calculation on top of the concrete itself: how much soil comes out of the hole, and how much of it, or imported fill, goes back in around the finished pour. Excavated soil expands as it's dug, typically by 15–30%, so the volume of spoil to haul away is noticeably more than the hole's plain dimensions suggest. The fill dirt and excavation calculator handles that swell factor directly, and is worth running before ordering a disposal bin or backfill material alongside the concrete itself.
Curing Time Before Loading a Slab
A pour's volume calculation is finished the moment the concrete truck leaves, but the slab itself isn't ready to use for some time after that. Concrete typically reaches enough strength to walk on within 24–48 hours, but standard guidance is to wait about a week before anything heavier, furniture, foot traffic in quantity, and closer to a full month before driving a vehicle onto it, since concrete continues gaining strength for roughly 28 days after the pour. Rushing this timeline is a common way a correctly-calculated, correctly-poured slab still ends up cracked or marked, for reasons that have nothing to do with the volume math on this page.
Weather at pour time also affects both the finished slab and how the order should be timed. Pouring in very hot or very dry conditions accelerates surface drying relative to the concrete curing underneath, which can crack the surface even on a well-calculated pour, many contractors schedule pours for early morning in summer specifically to avoid this. None of this changes the volume figure this calculator produces, but it's worth planning around once you have that number and are scheduling the actual delivery.
Ordering Ready-Mix: What to Tell the Plant
Once this calculator gives you a cubic-yard figure, a ready-mix order needs a few more specifics beyond the raw quantity. Plants typically ask for the mix strength (commonly written as, for example, "3000 PSI" or "4000 PSI" for residential slabs and footings respectively), the slump (how wet or stiff the mix is, affecting how easily it flows and finishes), and whether you need any additives, accelerator for cold-weather pours, retarder for hot weather or a longer haul distance, or fiber reinforcement as an alternative to steel mesh in a slab. None of these change the volume calculation, but getting them wrong on the order can mean a delivered load that's technically the right amount of concrete but the wrong mix for the job.
Most plants also have a minimum order, commonly around one cubic yard, and charge a short-load fee below that threshold, which is worth factoring in alongside the bagged-vs-ready-mix comparison covered above: a pour that calculates to 0.75 yd³ might cost nearly the same delivered as a full yard once the short-load fee is added, making it worth rounding the order up to the full yard rather than paying a premium for the smaller amount.
These figures estimate material quantities only. Slab thickness, reinforcement and footing depth for anything structural are set by your local building code and site conditions, check the requirements that apply where you are before you pour.
Reinforcement Doesn't Change the Volume Calculation
Steel rebar or wire mesh embedded in a slab or footing displaces a genuinely negligible fraction of the total pour volume, reinforcement is sized to resist tension and cracking, not to take up meaningful space, so this calculator's output doesn't need any adjustment to account for it. What reinforcement does affect is sequencing: rebar or mesh has to be placed and supported at the correct height within the form before the pour, which is a scheduling and labor consideration entirely separate from the volume math on this page.
Frequently Asked Questions
At what point does it make sense to switch from bagged mix to ready-mix delivery?
Around one cubic yard, that's about 60 bags of 60 lb mix, which is a full day of hand-mixing for most people. Below that, bagged concrete is usually more practical; above it, a ready-mix truck saves enough labor to be worth the delivery minimum.
Why add a waste factor to a concrete order?
Uneven subgrade, minor spillage during placement, and the difference between a form's nominal and as-built dimensions all eat into a precisely-calculated volume, a 10% margin covers most of that without meaningfully increasing cost, and running short mid-pour is far more expensive than a bit of surplus.
Do I need rebar for a slab this calculator sizes?
That depends on the slab's span, load and local building code, not on its volume, this calculator sizes material quantity only. Check your local code or a structural engineer for reinforcement requirements before pouring anything load-bearing. A small stepping-stone pour typically needs none at all, while a driveway slab almost always does.
How much does a 60 lb bag of concrete actually yield?
About 0.45 cubic feet once mixed, meaning it takes roughly 2.2 bags to make one cubic foot of finished concrete, and about 60 bags to make a full cubic yard. An 80 lb bag scales up proportionally to roughly 0.60 cubic feet, so a larger bag size changes the bag count, not the total volume needed.