How Many Bags of Concrete for a 10x10 Slab

If you are about to pour a 10x10 concrete slab, the first question on your list is probably a simple one: how many bags of mix do I need to buy? The answer for the standard 4-inch-thick patio slab is roughly 56 bags of 80 lb concrete, or about 62 bags once you add the waste factor most contractors recommend. But that number changes with the thickness of the slab and the size of the bag you choose, so it is worth understanding the math instead of trusting a single figure.

The Formula Behind the Answer

Concrete is ordered in one of two ways: by the bag for small DIY jobs, or by the cubic yard for anything delivered by a ready-mix truck. Both start with the same volume calculation. For a rectangular slab, the volume in cubic feet is:

Length (ft) x Width (ft) x Thickness (ft) = Cubic Feet

Your 10x10 slab has a footprint of 100 square feet. At 4 inches thick, convert the thickness to feet first (4 inches = 0.333 feet), then multiply: 10 x 10 x 0.333 = 33.3 cubic feet. Divide that by 27 (the number of cubic feet in a cubic yard) and you get 1.23 cubic yards of concrete for the slab.

Bags Per Cubic Yard

Bagged concrete is sold by weight, and the most common sizes are 40 lb, 60 lb, and 80 lb. Each size yields a different volume of finished concrete:

• 40 lb bag: yields about 0.30 cubic feet
• 60 lb bag: yields about 0.45 cubic feet
• 80 lb bag: yields about 0.60 cubic feet

Since a cubic yard is 27 cubic feet, it takes roughly 90 bags of 40 lb, 60 bags of 60 lb, or 45 bags of 80 lb to make one yard. Your 10x10 slab is 33.3 cubic feet, so here is the bag count for each size:

• 80 lb bags: 33.3 / 0.60 = 56 bags
• 60 lb bags: 33.3 / 0.45 = 74 bags
• 40 lb bags: 33.3 / 0.30 = 111 bags

That 56-bag figure assumes a clean, level pour with zero waste. Real subgrades are rarely perfect, so almost every contractor adds a 10% waste factor. Multiply 56 by 1.10 and you get about 62 bags of 80 lb mix. If you are mixing by hand in a wheelbarrow, that is a heavy day of work — 62 bags at 80 lb each is nearly 5,000 pounds of dry mix you have to haul, dump, and mix one at a time.

Thickness Changes Everything

The 4-inch slab is the most common for patios and walkways, but driveways are thicker. A 10x10 driveway at 5 inches needs 10 x 10 x 0.417 = 41.7 cubic feet, or about 70 bags of 80 lb mix (77 with waste). At 6 inches it jumps to 50 cubic feet, or 84 bags of 80 lb (92 with waste). The material cost rises roughly 50% going from 4 to 6 inches, so it pays to confirm your local code minimum before you buy. If you are unsure which thickness applies to your project, the slab thickness guide elsewhere on this site covers the load requirements for patios, driveways, and garage floors.

Bags vs. Ready-Mix Truck: The Money Question

Before you commit to 56 bags, it is worth pricing a truck. Your 10x10 slab at 4 inches is only 1.23 cubic yards — right around the practical crossover where bags stop making sense. Here is the comparison for a 1.4-yard order (your slab plus waste):

• Bags: 62 x $7 per 80 lb bag = $434 in material, plus a full day of mixing labor.
• Ready-mix: 1.4 yards at $160/yard = $224, plus a short-load fee of about $100 for a small order = $324 delivered.

Even with the short-load fee, the truck is often cheaper and always faster for a 10x10 slab. Many plants waive short-load fees above a 3-yard minimum, so if you can group a few small pours into one order, the truck wins decisively. Below about half a yard (a small pad or a couple of footings), bags are the clear choice; above it, price both before you commit.

Practical Mixing Tips

If you do go the bag route, work in batches you can actually finish. Mixing more than about 0.4 cubic feet at a time (roughly two-thirds of an 80 lb bag) in a wheelbarrow is miserable and leads to inconsistent batches. Rent or borrow a mixer if you can, and stage all 56 bags near the pour before you start. Have at least two people — one mixing, one placing and screeding — and work quickly, because concrete begins setting within about 90 minutes of adding water. Finally, never add extra water to make it easier to work; more water means weaker concrete. Keep the mix to the manufacturer's spec, compact the subgrade, and add the 10% buffer so you never run short on pour day.

For the exact figure on your own project, plug your length, width, and thickness into the concrete calculator at the top of this page. It converts your measurements to cubic yards, gives you the bag count for 40, 60, and 80 lb sizes, and adds the waste factor automatically.