Yardage concrete calculator
Any pour, straight to the cubic yards a plant quotes in.
Decimals fine. Bag counts round up.
At 20 × 20 ft and 4 inches you need
4.94 cubic yards
133.3 cubic feet · 18,670 lb of concrete · order 5.43 yd³ with the 10% waste allowance
Order ready-mix. At 4.94 yd³ you are 3.7 times past the point where bagging pays. That is one truck, one morning — against 223 bags to lift, mix and place before the first batch sets.
Two rules, each where it applies. Bag counts carry no waste allowance — a partial bag is not a thing you can buy, and an unopened one goes back — so the headline count is the volume and the figure beside it is the same count with waste. The ready-mix figure carries its allowance inside because a truck will not come back for a quarter yard.
The inch that costs $240
Thickness runs from the top of the compacted gravel to the finished surface. Measure from the dirt and you count the base as concrete: on this pour, one inch of that error is 1.23 extra cubic yards — about $240 of ready-mix, or 56 bags nobody needed. Set a stake to the finished height before you order.
The arithmetic, in the open
How this page gets its numbers
- Volume, cubic feet
- 20 × 20 × (4 ÷ 12) = 133.3 ft³
- Cubic yards
- 133.3 ft³ ÷ 27 = 4.94 yd³
- 80 lb bags
- ceiling(133.3 ÷ 0.60 ft³ a bag) = 223 bags, no waste allowance; with 10% waste, 245
- 60 lb bags
- ceiling(133.3 ÷ 0.45 ft³ a bag) = 297 bags, no waste allowance; with 10% waste, 326
- Weight
- 133.3 ft³ × 140 lb per ft³ = 18,670 lb
- Order allowance
- 4.94 yd³ plus 10% = 5.43 yd³ ordered
- Truck loads
- ceiling(5.43 yd³ ordered ÷ 10 yd³ a load) = 1 — a full truckload is typically about 10 cubic yards
Bag counts round up. A partial bag is not a thing you can buy, so a calculated 222.2 bags is 223 bags.
Yardage presets
The 6 sets people ask for most
| Slab | Area ft² | Cubic yards | 80 lb bags→ with 10% waste | Buy as |
|---|---|---|---|---|
| 20 × 30 ft | 600 | 7.41 | 334→367 | Ready-mix |
| 24 × 24 ft | 576 | 7.11 | 320→352 | Ready-mix |
| 30 × 30 ft | 900 | 11.11 | 500→550 | Ready-mix |
| 30 × 40 ft | 1,200 | 14.81 | 667→734 | Ready-mix |
| 40 × 40 ft | 1,600 | 19.75 | 889→978 | Ready-mix |
| 40 × 60 ft | 2,400 | 29.63 | 1,334→1,467 | Ready-mix |
A different shape
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Asked about this shape
Questions
How much concrete does 20 × 20 ft and 4 inches take?
4.94 cubic yards, which is 133.3 cubic feet before any allowance. Order 5.43 yd³ to carry the 10% waste.
What does that much concrete cost?
About $830 to $1,120 for the mix delivered, at $180 per cubic yard on 5.43 ordered yards. Replace the price with your own quote — it is the one number on this page that moves with where you live.
Why do plants quote in cubic yards?
Because a drum is loaded by volume and a yard is the unit the industry settled on. One cubic yard is 27 cubic feet, so a figure in feet divides by 27 to become the number you say on the phone.
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.
How much extra should I order?
10 percent, and where it appears depends on what you are buying. Ready-mix carries it inside the ordered figure, because a truck will not come back for a quarter yard. Bag counts do not: the headline count is the volume, and the plus figure sits beside it, because bags are bought one at a time and an unopened one goes back. Either way the allowance covers spillage, a base that is not perfectly flat and the thickness you gain at the edges of the form.
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.
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.
Updated 2026-08-25