Concrete calculator: the yards and the bags, ready to quote
Length times width times thickness, divided by 12 and then by 27, is the cubic yards. Add what you order on top, round up to what the plant sells, and you have a line for a quote. In the example below a driveway and its walk come to 8.5 cubic yards to order.
Count the concrete
Type what is being poured: slabs, footings, round holes, or all three. You get the cubic yards to order, the same pour in bags, and lines to put on a quote.
Slabs
A driveway, a patio, a walk, a pad. A new row opens when the last one is filled.
What the plans or the customer call for. This page does not say how thick a slab should be.
Footings
Long and narrow, so the width and the depth are in inches. Leave these empty if there are none.
Round holes or forms
All the same size. Leave these empty if there are none.
The order
So the pour does not come up short. It starts at 10; put in your own.
Printed on the bag. It starts at 0.6, one maker's 80 lb bag. Empty it to count ready-mix only.
Type the length, the width and the thickness of a slab, or fill in a footing or a hole. The count shows here.
A driveway and a walk, counted
An example with made-up numbers, not a going rate
Say a driveway is 12 by 40 feet and the walk beside it 4 by 30, and the plans call for 4 inches. That is 480 and 120 square feet: 600 in all. As poured it is 200 cubic feet, which is 7.41 cubic yards. Say you order 10% extra: 8.15 yards, so 8.5 go on the quote. From bags that yield 0.6 cubic feet each, the same pour with its extra would be 367 bags.
How it is worked out
- A slab: length times width is the square feet. Square feet times the thickness in inches, divided by 12, is the cubic feet.
- A footing: the same sum, with the width in inches divided by 12 first.
- A round hole or form: half its width, squared, times pi, is the circle. Times the depth it is the volume of one, and times how many it is all of them.
- Cubic feet divided by 27 is cubic yards: 27 cubic feet make 1 cubic yard.
- The extra goes on top. The ready mixed concrete producers' association says to order 4% to 10% more than the plan dimensions give, to account for contingencies: National Ready Mixed Concrete Association, CIP 31: Ordering Ready Mixed Concrete.
- For bags, the cubic feet are divided by what one bag yields, and part of a bag is a whole bag. QUIKRETE's own calculator rounds up the same way, and says its yields do not allow for uneven ground or waste. So the bags are shown twice: as poured, and with your extra.
What a bag yields
- QUIKRETE's data sheet for its concrete mix gives, for one bag: about 0.30 cubic feet from 40 lb, 0.375 from 50 lb, 0.45 from 60 lb, 0.60 from 80 lb and 0.675 from 90 lb.
- At those yields a cubic yard is 90 bags of 40 lb, 72 of 50 lb, 60 of 60 lb, 45 of 80 lb or 40 of 90 lb. That is 27 divided by the yield.
- Sakrete gives the same figures for the 40, 60 and 80 lb bags of its high-strength mix.
- Another mix can yield something else. The figure is printed on the bag: type that one.
- Both makers give their mix for pours 2 inches thick or more. That is a maker's line about its own product, and the counter repeats it when a slab is thinner. It is not a thickness for your slab.
The order is rounded up, never down
Ready-mix is sold by volume, in cubic yards, and a truck mixer holds 8 to 12 of them, the producers' association says. It also says to avoid ordering small clean-up loads: the same sheet.
So the line for the order goes up to the next half yard. The half is our choice, because a step had to be picked. Ask your plant how small a step it sells and what it charges to bring less than a full load, and put that charge on the quote too.
Bags or a truck is your call. This page counts both and prices neither.
What this count is not
- It is not a design. Nothing here says how thick a slab should be, what goes under it or what steel goes in it. That comes from the plans, an engineer or your building department.
- It is not an order. A count from measurements is an estimate: check it against the forms on the day of the pour.
- It does not price anything. TailGateBid has no price data, and the box for what a yard costs you is on the page that prices the slab.
From the count to the quote
The lines under the calculator are written the way a quote takes them: a quantity, a unit and a name. The pour is counted by the square foot and the concrete by the cubic yard, so both grow with the job.
Next, work out what to charge for the slab from the same measurements, your own price for a yard and your crew's hours. Or put the lines on an estimate and print it.
TailGateBid for concrete work has a patio quote worked through, and in the app the same lines go on a quote your customer signs on their phone.
Where each number comes from
- A cubic yard is 27 cubic feet. That is how feet of length and width, and a depth, become cubic yards.
- The box for the extra to order starts at 10 percent. The ready mixed concrete producers' association says to order 4 to 10 percent more than the plan dimensions give. Starting at the top of that range is our choice. National Ready Mixed Concrete Association, CIP 31: Ordering Ready Mixed Concrete, . (our choice, change it)
- The cubic yards to order are rounded up to the next 0.5 of a yard. That step is our choice, not a rule. Ask your ready-mix plant how small a step it sells.
- The box for what one bag yields starts at 0.6 cubic feet. That is what QUIKRETE's data sheet gives for an 80 lb bag of its concrete mix; the same sheet gives 0.30 for a 40 lb bag, 0.375 for 50 lb, 0.45 for 60 lb and 0.675 for 90 lb. Starting at the 80 lb bag is our choice. Type the yield printed on the bag you buy. QUIKRETE, Concrete Mix data sheet (no. 1101), . (our choice, change it)
- QUIKRETE's data sheet says its concrete mix is for pouring concrete 2 inches thick or more. Where a slab typed here is thinner, the count still shows, with a line that says so. This page gives no thickness for any use. QUIKRETE, Concrete Mix data sheet (no. 1101), .
On a TailGateBid quote the pour is a line by the square foot and the concrete a line by the cubic yard, each with your own price.
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Sources
- National Institute of Standards and Technology, Handbook 44 (2026), Appendix C,
- National Ready Mixed Concrete Association, CIP 31: Ordering Ready Mixed Concrete,
- QUIKRETE, Concrete Mix data sheet (no. 1101),
- QUIKRETE, the notes on its own concrete calculator,
- Sakrete, High-Strength Concrete Mix product page,
Related
- Concrete slab or drivewaySquare feet sold and cubic yards bought: the concrete, the crew's hours and the rest, worked into a price for a square foot.
- ConcreteSquare feet and cubic yards on a quote your customer signs on their phone.
- Estimate makerType a few lines and print a clean estimate or quote, in English or Spanish. Nothing you type is sent anywhere.
- Job price16 hours of work and $600 of materials cost you $1,320. See what five prices would leave you.
By TailGateBid. .
A count is as good as the measurements you type. What is printed on the bag, the can or the pail you buy decides, and so do the plans.