How many bags of concrete for a 10x10 slab?
A 10 by 10 foot slab poured 4 inches thick, with a 10 percent waste factor, needs 123 bags of 40 lb concrete mix, 82 bags of 60 lb mix, or 62 bags of 80 lb mix. That is 36.67 cubic feet of material to order, which is about 1.36 cubic yards.
Those figures use the published yields for QUIKRETE Concrete Mix (40 lb = 0.30 cubic feet, 60 lb = 0.45 cubic feet, 80 lb = 0.60 cubic feet), each bag count rounded up since you cannot buy a partial bag.
The full arithmetic
| Slab footprint | 10 ft × 10 ft = 100 sq ft |
| Thickness in feet | 4 in ÷ 12 = 0.333 ft |
| Volume | 100 × 0.333 = 33.33 cu ft |
| Plus 10 percent waste | 33.33 × 1.10 = 36.67 cu ft |
| Cubic yards | 36.67 ÷ 27 = 1.36 cu yd |
| 40 lb bags (0.30 ft³ each) | 36.67 ÷ 0.30 = 122.2, round up to 123 bags |
| 60 lb bags (0.45 ft³ each) | 36.67 ÷ 0.45 = 81.5, round up to 82 bags |
| 80 lb bags (0.60 ft³ each) | 36.67 ÷ 0.60 = 61.1, round up to 62 bags |
Run your own numbers, including other slab sizes and footings, in the concrete calculator.
Bag counts by slab thickness
A 10x10 slab does not have to be 4 inches thick. Volume scales directly with thickness, so the bag count scales the same way. All rows below use a 10 percent waste factor.
| Thickness | Volume with waste | 40 lb bags | 60 lb bags | 80 lb bags |
|---|---|---|---|---|
| 3 in | 27.50 cu ft | 92 | 62 | 46 |
| 4 in (standard) | 36.67 cu ft | 123 | 82 | 62 |
| 5 in | 45.83 cu ft | 153 | 102 | 77 |
| 6 in | 55.00 cu ft | 184 | 123 | 92 |
4 inches is standard for a patio, shed base, or walkway. Driveways and anything that carries vehicle weight are usually poured 5 to 6 inches thick or more, with rebar or wire mesh reinforcement, which this calculation does not include.
Why bag size changes the count, not the material
All three bag sizes are the same QUIKRETE Concrete Mix product, just packaged differently, and each one resolves to roughly the same total weight of dry mix. One cubic yard (27 cubic feet) takes 90 bags of 40 lb mix, 60 bags of 60 lb mix, or 45 bags of 80 lb mix, and all three come out to about 3,600 lb. That consistency is a useful sanity check: if your bag counts for the same job do not scale in that ratio across sizes, recheck the math.
Smaller bags are easier to carry and mix by hand in a wheelbarrow or mixing tub, but you handle more of them. An 80 lb bag halves the bag count of a 40 lb bag for the same job, at roughly double the weight per bag.
What would change this number
- Thickness. The single biggest factor. Check your form height or screed guide in more than one spot before ordering.
- Waste factor. 10 percent covers a level, compacted sub-grade. Uneven or poorly compacted ground, hand mixing in small batches, or pouring in stages are all reasons to go to 15 or 20 percent.
- Sub-grade preparation. Low spots and voids in the base soak up extra material you cannot see until you are already pouring, which is exactly what the waste factor is meant to cover.
- Pour size. At roughly 1.36 cubic yards, this job sits right at the point where it is worth calling a local ready-mix supplier for a delivered price, since delivery is often cheaper and far less labor once a pour approaches a full cubic yard.
Frequently asked questions
How many bags of concrete do I need for a 10x10 slab?
For a 10 by 10 foot slab poured 4 inches thick with a 10 percent waste factor, you need 123 bags of 40 lb mix, 82 bags of 60 lb mix, or 62 bags of 80 lb mix. That works out to 36.67 cubic feet of material, or about 1.36 cubic yards.
How many 80 lb bags of concrete for a 10x10 slab 4 inches thick?
62 bags. The slab needs 36.67 cubic feet of concrete after a 10 percent waste factor, and each 80 lb bag yields about 0.60 cubic feet, so 36.67 divided by 0.60 is 61.1, rounded up to 62 whole bags.
How many 60 lb bags of concrete for a 10x10 slab?
82 bags, at the standard 4 inch thickness with 10 percent waste. Each 60 lb bag yields about 0.45 cubic feet, so 36.67 divided by 0.45 is 81.5, rounded up to 82 bags.
How many 40 lb bags of concrete for a 10x10 slab?
123 bags, at the standard 4 inch thickness with 10 percent waste. Each 40 lb bag yields about 0.30 cubic feet, so 36.67 divided by 0.30 is 122.2, rounded up to 123 bags.
Does the bag count change if my 10x10 slab is thicker than 4 inches?
Yes, directly and proportionally. A 10x10 slab at 6 inches thick needs 184 bags of 40 lb mix, 123 bags of 60 lb mix, or 92 bags of 80 lb mix with the same 10 percent waste factor, roughly half again as much as the 4 inch version. Always confirm your form or screed height before ordering.
How much waste factor should I add to a 10x10 slab?
10 percent is a reasonable default for a slab on a level, compacted sub-grade. Push it to 15 or 20 percent if the ground is uneven, not fully compacted, or if you are hand-mixing in small batches that vary from batch to batch.