How many bags of concrete for a 10×10 slab?
A 10 × 10 ft slab at the common 4-inch thickness needs about 1.23 cubic yards of concrete — roughly 56 bags of 80 lb mix (or 74 × 60 lb, or 111 × 40 lb). At this size, many people order a small ready-mix load instead of mixing dozens of bags by hand. Here's the math, plus the base, reinforcement, and budget that go with it.
The math
- Area = 10 × 10 = 100 sq ft
- Volume = 100 × (4 ÷ 12) = 33.3 cu ft = 33.3 ÷ 27 = 1.23 cubic yards
- Bags = 33.3 cu ft ÷ the bag's yield (80 lb = 0.60 cu ft) = ~56 bags of 80 lb
By slab thickness
| Thickness | Cubic yards | 80 lb bags |
|---|---|---|
| 4 inches | 1.23 cu yd | ~56 |
| 5 inches | 1.54 cu yd | ~70 |
| 6 inches | 1.85 cu yd | ~84 |
Always buy a little extra (about 5–10%) for uneven subgrade and spillage. Four inches suits patios, walkways, and shed floors; go 5–6 inches where a vehicle will park.
Different size or thickness?
The concrete calculator gives cubic yards and the bag count for any slab, footing, or post — with an editable price.
Open the Concrete CalculatorWhat goes under (and inside) the slab
The concrete is only the top layer of the build. For a 10×10 slab plan on:
- Compacted gravel base, ~4 inches: about 1.2 cubic yards (≈1.7 tons) of crushed stone over firm, undisturbed soil — it drains water away and spreads loads so the slab doesn't settle and crack.
- Forms: four 10-ft 2×4s staked dead level around the perimeter, with the top edges as your screed guide.
- Vapor barrier: a 6-mil plastic sheet under slabs that will be enclosed (shed, workshop) to stop ground moisture wicking up.
- Reinforcement: welded-wire mesh (two to three 5×10 ft sheets, overlapped ~6 inches and propped mid-slab on chairs) or a fiber-reinforced mix. Rebar grids are for thicker, loaded slabs — the rebar calculator sizes a grid if you go that route.
One code note: a slab for a small detached shed is often permit-exempt, but attached structures, garages, and anything habitable usually trigger permits and frost-depth footings — a quick call to your building department is free.
What it costs at this size
This is the rare job where bags and the truck cost about the same money — the difference is your back:
- Bags: 56 × 80 lb at $5–$8 each ≈ $280–$450, plus mixer rental if you're smart about it.
- Ready-mix: ~1.3 yards at $140–$200/yd plus a $60–$150 short-load fee ≈ $235–$450 delivered.
Since the totals overlap, ready-mix usually wins here: no hauling two-plus tons of bags, and the whole slab pours wet-on-wet. See bags vs. ready-mix for the full crossover math.
Pouring-day basics
A 10×10 pour is very doable for two or three people, but concrete doesn't wait: have the base compacted, forms braced, mesh placed, and tools staged before the truck arrives (drivers typically allow a few minutes per yard before standby charges). Screed off the form tops, bull-float once, then let the bleed water disappear before finishing. Curing: keep the surface damp, stay off it for 24–48 hours, give it about a week before heavy loads or framing, and expect full design strength at ~28 days. Misting or covering the slab for the first few days makes measurably stronger concrete.