BuildCalc Guides · Concrete
How Many Bags of Concrete for an 8×10 Slab?
An 8 by 10 foot pad — shed floor, hot-tub base, generator pad or small patio — is one of the most common DIY concrete jobs. Here is the short answer and the exact math.
The math
Concrete is priced and ordered in cubic yards, but the math starts in cubic feet. For an 8 by 10 foot slab at 4 inches thick:
- Volume in cubic feet = length × width × depth, all in feet. 8 × 10 × (4 ÷ 12) = 26.67 ft³.
- Cubic yards = cubic feet ÷ 27. 26.67 ÷ 27 = 0.99 yd³ net.
- Add waste. 0.99 × 1.05 = 1.04 yd³ to order in bulk.
- Convert to bags. An 80 lb bag yields about 0.6 ft³, a 60 lb bag about 0.45 ft³. With 5 percent waste folded in, that is 47 bags of 80 lb or 63 bags of 60 lb.
By slab thickness
An 8×10 is poured at 3, 4 or 6 inches depending on what sits on it. Bag count scales directly with depth:
| Thickness | ft³ | yd³ | 80 lb bags | 60 lb bags |
|---|---|---|---|---|
| 3" | 20.0 | 0.74 | 35 | 47 |
| 4" | 26.7 | 0.99 | 47 | 63 |
| 6" | 40.0 | 1.48 | 70 | 94 |
Includes a 5 percent waste factor and rounds up to whole bags.
Bags or ready-mix?
An 8×10 sits at the low end of the ready-mix range — about a yard for a 4 inch pad. Here is how the call usually goes:
- Bags win when access is the problem (no truck path), the job is under about 1 yd³, or you want to mix at your own pace. Downside: mixing 47 bags takes 3 to 5 hours with a wheelbarrow mixer.
- Ready-mix wins the moment you have truck access. Most suppliers charge a short-load fee under 3 yd³, but the all-in cost is often within $50 of bagged — for a 30 minute pour instead of half a day.
Calculate for your own slab
The numbers above are for a standard 8′ × 10′ × 4″ pad. For any other size, depth or bag — including footings and round sonotube columns — BuildCalc's concrete calculator handles fractional input, waste factor and live material cost.
Open the concrete calculator →FAQ
How many cubic yards of concrete is an 8x10 slab?+
An 8 by 10 foot slab at 4 inches thick is about 0.99 cubic yards of net concrete. Add a 5 percent waste allowance and you would order about 1.04 cubic yards.
How thick should an 8x10 concrete slab be?+
4 inches handles a patio, shed pad or hot-tub deck. Step up to 6 inches if anything heavier than foot traffic will sit on it — a small structure, a workbench with a vise, or a vehicle wheel. 3 inches is fine for sidewalks and paver bases.
Is 1 yard of concrete enough for an 8x10 pad?+
Just barely at 4 inches — the net volume is 0.99 yd³, so any waste at all pushes you over. Order 1.1 to 1.25 yd³ to be safe, or plan to top off with a bag or two if you go ready-mix.
Is bagged concrete cheaper than ready-mix for an 8x10 slab?+
At about 1 cubic yard, bagged usually costs the same or more once you total 47 bags vs. a short-load delivery. Bagged still wins when the truck cannot reach the site or you want to pour in stages. For one continuous pour at this size, ready-mix is generally faster and not much more expensive.
How much waste should I add for a small slab?+
Add at least 5 percent — that covers normal spillage and minor over-excavation. The bag counts in the table above already include 5 percent. For rough or hand-dug subgrade, push it to 10 percent.
Do I need rebar in an 8x10 slab?+
For a 4 inch patio or shed pad, a sheet of welded wire mesh or #3 rebar at 16 to 24 inch on-center is standard — it controls cracking more than it adds strength. For driveways and heavier slabs, step up to #4 rebar at 12 to 16 inch on-center.
Related guides
- How many bags of concrete for a 10×10 slab? — the next-size-up clone, with the bag-vs-truck math.
- How many bags of concrete for a 12×12 slab? — most common patio size.
- How many bags of concrete for a hot-tub pad? — sizing the 6 inch slab a tub needs.