8 concrete calculators

One per shape, because the measurements are different and a single form with thirteen modes helps nobody standing in a trench. All of them use the same constants: 0.60 ft³ an 80 lb bag, 0.45 ft³ a 60 lb bag, 140 lb a cubic foot, a full truckload typically about 10 cubic yards, and bag counts rounded up with the 10% waste figure beside them.

By shape

Pick the shape you are pouring

SlabWidth, length, thickness — patios, sheds, driveways YardageAny pour, straight to cubic yards BagsHow many 40, 50, 60, 80 or 90 lb bags CostYards at your quoted price PremixBag yields for the mix you actually bought WeightWhat the pour weighs, for hauling and forms SonotubeDiameter and height, per tube and per job Strip footingTrench width, depth and total run

By what you already know

If you have this, and want that

8 calculators, sorted by the measurement you are holding rather than by name.
What you have	What you want	Go to
A width, a length and a thickness	Cubic yards and bags	Slab
Any pour, already measured	Cubic yards, the way a plant quotes	Yardage
A volume and a bag size	How many bags at 40, 50, 60, 80 or 90 lb	Bags
A quoted price per yard	What the concrete costs at that price	Cost
A bag brand and its stated yield	Bags for your volume at that yield	Premix
A finished pour	What it weighs, for hauling and forms	Weight
A tube diameter and a height	Yards per tube and for the job	Sonotube
A trench width, depth and run	Yards for a continuous footing	Strip footing

Not sure which? The the slab calculator covers anything flat, and it is the one most people need.

Sizes, not shapes

Already know the size?

All 111 slab sizesArea, yards at 4 in and 80 lb bags, no typing Any dimensionsType a width, a length and a thickness How to measureBefore you trust any of these numbers

The same in every calculator

Questions

How many 80 lb bags are in a cubic yard?

45, and you buy 45. An 80 lb bag of mix yields about 0.60 cubic feet once water is in it, and a cubic yard is 27 cubic feet. A 60 lb bag yields about 0.45 cubic feet, so 60 of those make a yard. Every bag count on this site is rounded up, because a store will not sell you nine tenths of a bag.

Bags or ready-mix — where is the line?

Around 60 bags of 80 lb, which is 36 cubic feet or 1.33 cubic yards. Under that you can mix it in a day with a rented mixer and one helper, and you pay only for what you open. Over it you are buying several pallets, handling two tons or more by hand, and racing the set on the first batch you placed. Some plants charge a short-load fee below about 3 yards, so ask when you book.

What is a mixer-truck load?

A full truckload is typically about 10 cubic yards, and that is the figure this site plans with. Ask when you book: drums vary, and a plant will tell you what it is sending. The load count here is worked from the ordered volume — the one that already includes the 10% allowance — because that is what actually has to fit on the truck.

Where exactly do I measure thickness from?

From the top of the compacted gravel base to the finished surface of the slab. The gravel is not concrete, and the mistake is expensive: one inch of it counted as concrete on a 20 × 20 ft slab is 1.23 cubic yards. Compact the base, set a stake to the finished height, and measure down from that.

Does this include rebar, forms or labour?

No. The price band is concrete delivered: your own price per yard on the ordered volume, taken 15% either side of the middle to cover what a quote actually varies by. Forms, gravel, mesh or bar, a pump if the truck cannot reach, and finishing are all separate. Get the plant to quote your postcode before you budget.

Bag yields: QUIKRETE Concrete Mix data sheet No. 1101. Price basis: Concrete Financial Insights weighted average selling price for 2025, escalated with U.S. Bureau of Labor Statistics PPI series PCU327320327320 (2026-07). Prices vary by region — enter your own quote above.