KLM Labs

How many bags of concrete in a yard?

It takes about 45 bags of 80 lb concrete to make a cubic yard, 60 bags of 60 lb or 90 bags of 40 lb. With 10% extra for waste, buy 50, 66 or 99.

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Page 1 of the printable concrete bags per yard, and slab chart: Premixed bags per cubic yard by bag size, and cubic yards and 80 lb bags for common slabs with 10% waste. — The printable chart. US Letter, 1 page.

Bags of premixed concrete in one cubic yard

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Bag	Yield per bag	Bags per cubic yard	With 10% waste
80 lb	0.6 cu ft	45	50 (49.5)
60 lb	0.45 cu ft	60	66
40 lb	0.3 cu ft	90	99

A cubic yard is 27 cubic feet. Bag counts are rounded up; the exact figure is in brackets.

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Concrete for a slab (with 10% waste)

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Slab	4" thick: cu yd	4" thick: 80 lb bags	6" thick: cu yd	6" thick: 80 lb bags
8' × 8'	0.87	40	1.3	59
10' × 10'	1.36	62	2.04	92
10' × 12'	1.63	74	2.44	110
12' × 12'	1.96	88	2.93	132
12' × 16'	2.61	118	3.91	176
10' × 20'	2.72	123	4.07	184
12' × 20'	3.26	147	4.89	220
16' × 16'	3.48	157	5.21	235
20' × 20'	5.43	245	8.15	367
24' × 24'	7.82	352	11.73	528

Cubic yards to 2 decimal places. Bag counts are rounded up.

How many yards of concrete is a 12x12 slab?

A 12' × 12' slab 4" thick is 12 × 12 × 4/12 = 48 cubic feet, which is 1.78 cubic yards. With 10% for waste it is 1.96 cubic yards, or 88 bags of 80 lb concrete. At 6" thick it takes 2.93 cubic yards with waste, or 132 bags.

How many bags of concrete for a 10x10 slab?

At 4" thick, a 10' × 10' slab is 33.33 cubic feet. With 10% waste that is 36.67 cubic feet, 1.36 cubic yards, or 62 bags of 80 lb concrete (61.11 exactly, rounded up). With no waste it is 56 bags.