Guides · Concrete
How Many Bags of Concrete Do I Need for a 10×10 Slab? (60 lb vs 80 lb Layouts)
By the MyBuildCalcHub team · Figures verified against our audited estimating engine · Updated
The math behind the answer
Concrete volume is length × width × thickness, with everything in the same unit. A 10×10 slab at 4 inches: 10 × 10 × (4 ÷ 12) = 33.33 cubic feet. Divide by 27 to get 1.23 cubic yards. Bag counts come from each bag's mixed yield, which is printed on the bag and consistent across major brands: an 80 lb bag yields 0.60 ft³, a 60 lb bag 0.45 ft³, and a 40 lb bag 0.30 ft³. Divide the slab volume by the yield and round up, always up, because you can't buy 0.6 of a bag, and running short mid-pour creates a cold joint (a permanent weak seam where fresh concrete meets concrete that already started setting), and cold joints are exactly where a slab later cracks.
Bag counts by slab thickness (10×10 slab)
Thickness is the decision that moves your order most, our coverage-per-yard guide shows the same relationship from the other side. Four inches is the residential standard for patios and shed bases; 5–6 inches is the heavy-duty spec where cars, trucks, or equipment will sit:
| Thickness | Volume | Cubic yards | 80 lb bags (+10% waste) | 60 lb bags (+10% waste) |
|---|---|---|---|---|
| 3.5 in (light foot traffic) | 29.2 ft³ | 1.08 | 49 (54) | 65 (72) |
| 4 in (patio / shed standard) | 33.3 ft³ | 1.23 | 56 (62) | 75 (82) |
| 5 in (light vehicle) | 41.7 ft³ | 1.54 | 70 (77) | 93 (102) |
| 6 in (driveway / heavy duty) | 50.0 ft³ | 1.85 | 84 (92) | 112 (123) |
60 lb vs 80 lb: which bag should you buy?
Same concrete, different lifting math. 80 lb bags mean fewer bags to buy, haul, and mix, 45 per cubic yard versus 60 for the 60 lb size, so crews default to them. 60 lb bags earn their place when the pour is a one-person job, the mixing station is far from the truck, or repeated 80 lb lifts simply aren't happening that day. There is no strength difference at the same mix rating; buy whichever your back and your helper count can handle, and don't mix sizes mid-pour if you can avoid it, consistent water ratios are easier with one bag size.
Bag counts for other common slab sizes (4 in thick)
| Slab size | Cubic yards | 80 lb bags (+10%) | 60 lb bags (+10%) |
|---|---|---|---|
| 8 × 8 ft | 0.79 | 36 (40) | 48 (53) |
| 10 × 10 ft | 1.23 | 56 (62) | 75 (82) |
| 10 × 12 ft | 1.48 | 67 (74) | 89 (98) |
| 12 × 12 ft | 1.78 | 80 (89) | 107 (118) |
| 20 × 20 ft | 4.94 | 223 (245) | 297 (326) |
The honest threshold: when bags stop making sense
Here's the number the bag aisle won't tell you: 62 eighty-pound bags is nearly 5,000 pounds of material, two and a half tons to load, transport, stage, and mix roughly one wheelbarrow at a time. A 10×10 slab sits right at the industry's practical crossover of about one cubic yard, past which most pros order ready-mix delivered by truck. Ready-mix arrives at a consistent water ratio, arrives all at once (no cold joints between batch 30 and batch 31), and turns a brutal all-day mixing marathon into a two-hour finishing job. Bags still win for smaller pours, staged work, and sites a truck can't reach.
Three mistakes that ruin the estimate
First, measuring thickness optimistically: subgrade is never perfectly level, and a slab that averages 4.5 inches instead of 4 quietly consumes 12% more concrete, this is half of why the 10% waste factor exists. Second, forgetting thickened edges: many shed and garage slabs call for a deeper perimeter footing, which is additional volume your flat-slab math misses. Third, skipping the waste factor to save a few bags: leftover concrete costs you a couple of bags; running short costs you a cold joint through your finished slab, our full guide to the 10% waste rule breaks down exactly why that buffer is non-negotiable. That trade is never worth it.
Frequently asked questions
How many 80 lb bags of concrete do I need for a 10x10 slab?
A 10x10 slab at the standard 4-inch thickness needs 56 eighty-pound bags, 62 once you add the industry-standard 10% waste factor. Each 80 lb bag yields 0.60 cubic feet, and a 10x10x4-inch slab is 33.3 cubic feet of concrete.
Is it cheaper to use bags or order ready-mix for a 10x10 slab?
A 10x10 slab sits right at the practical crossover. At 1.23+ cubic yards and roughly 62 bags to haul and mix, most homeowners come out ahead ordering ready-mix by truck: the pour arrives consistent, arrives all at once, and eliminates the cold-joint risk of mixing 62 batches by hand.
How thick should a 10x10 concrete slab be?
A 10x10 concrete slab should be 4 inches thick, the residential standard for patios, shed bases, and walkways. Go to 5-6 inches if vehicles will drive or park on it, and thicken the edges for shed or garage slabs. Footing depths are governed by your local frost line, so confirm with your building department.