Concrete for a 10×12 slab
A 10×12 ft slab at 4″ thick needs about 74 × 80 lb bags of concrete mix (with 10% waste) — or 1.75 cubic yards of ready-mix. Estimated materials cost ≈ $289 (ready-mix). Big enough to live on, small enough that the short-load fee still decides bags vs a truck.
| Area | 120 sq ft |
|---|---|
| Volume | 40 ft³ = 1.48 cu yd |
| 80 lb bags (no waste) | 67 |
| 80 lb bags (10% waste) | 74 |
| 60 lb bags (10% waste) | 98 |
| Ready-mix | 1.75 cu yd |
| Finished slab weight | ≈ 5,600 lb |
| Recommended | Order ready-mix |
What a 10×12 slab is usually for
- Small dining patio
- Workshop shed floor
- Play-equipment base
- Garden office footprint
120 square feet is roughly the smallest slab that works as a genuine dining patio — a four-seat table with chairs pushed back needs about 10 by 10 of clear space, so the extra 2 feet here is the difference between usable and cramped. If it is going under a garden room or a home office pod, check the supplier's bearing requirement, because habitable structures often want a thickened edge that a plain 4 inch slab does not give you.
Adjust it
Change the size, thickness, bag size, or waste % below:
How much concrete do I need?
| Bags (with overage) | |
|---|---|
| Bags (no overage) | |
| Ready-mix (delivered) | |
| Estimated materials cost |
Estimate for standard concrete mix (e.g. Quikrete #1101 / Sakrete High-Strength). Bag counts round up and include your overage %. Cost is an estimate (as of June 2026, US national average) — confirm bag price and ready-mix delivery (often a 1 yd³ minimum + short-load fees) with your supplier. Not a substitute for a structural engineer on load-bearing work.
Bags or a truck for this 10×12 patio
At 1.48 cubic yards, this slab sits in the awkward middle band where the short-load fee decides it. Here is the comparison with the fees included:
| Route | What you order | Estimated cost |
|---|---|---|
| Bags (80 lb) | 74 bags at ≈ $6.50 each | ≈ $481 |
| Ready-mix delivered | 1.75 yd³ at ≈ $165/yd³ , plus a short-load fee | ≈ $339–$439 |
Ready-mix is the better call at this size, even carrying the short-load fee. Beyond the price, a truck delivers the whole slab as one continuous placement — no cold joints between batches, no risk of the first section setting while you mix the last, and a consistent mix throughout. Mixing 74 bags to match it is a full day of heavy work with a worse result.
The short-load fee is what people miss. Suppliers charge it below roughly 4 cubic yards, typically $50–$150, because sending a truck out costs them the same whether it is full or not. Always ask for the delivered total including fees rather than the per-yard rate. The full reasoning is in bags vs ready-mix concrete.
Control joints so a 10×12 patio cracks where you choose
Concrete shrinks as it cures and it will crack — the only question is whether it cracks where you decided or where it chose. Control joints are the decision. The rule of thumb is a maximum spacing in feet of about two to three times the slab thickness in inches, so at 4″ that is 8–12 ft.
At 10×12 this slab fits inside a single panel at the maximum allowed spacing, so the rule does not force any joints on you. That said, a hard-freeze climate or a subgrade you are not confident about is a good reason to cut one anyway — a tooled joint disappears within a season, whereas a random shrinkage crack is permanent. The sequence is in forming and pouring a small slab.
How thickness changes a 10×12 slab
Thickness is the one input that changes the order most, and it is chosen by what will sit on the slab rather than by budget. Here is the same 120 sq ft footprint at each common depth:
| Thickness | 80 lb bags | Ready-mix | Est. materials | Typical use |
|---|---|---|---|---|
| 3.5″ | 65 | 1.5 yd³ | ≈ $248 | What a nominal 4″ pour often actually measures |
| 4″ (this page) | 74 | 1.75 yd³ | ≈ $289 | Patios, sheds, walkways, foot traffic |
| 5″ | 92 | 2.25 yd³ | ≈ $371 | Cars, light trailers, frequent vehicle use |
| 6″ | 110 | 2.5 yd³ | ≈ $413 | Trucks, RVs, machinery, heavy loads |
Going from 4″ to 6″ on this slab adds roughly $124 in materials — about 43% more. That is the entire cost of the decision, and it is why the advice for anything carrying a vehicle is to just pour the extra inches. Removing and replacing a cracked slab costs many times the difference.
The 3.5″ row is not a recommendation, it is a reality check: a “4 inch” slab poured on a subgrade that is a little high in places genuinely finishes at 3.5″ in those spots. If your base is not dead flat, order to the thicker figure. More on this in concrete slab thickness: 4″ vs 6″.
Pouring a 10×12 patio: the practical plan
| Wheelbarrow loads | ≈ 14 (at 3 ft³ each — weight-limited, not volume-limited) |
|---|---|
| Mixer batches | ≈ 37 at 2 bags per batch |
| Rough mixing time | ≈ 3.1 hours of continuous mixing, one person |
| Finished weight | ≈ 5,600 lb on the ground |
Be honest about that number.74 bags is past the point where a one-person mix-and-pour produces a good slab. Concrete starts stiffening within about 30 to 60 minutes in warm weather, so a long mixing session leaves cold joints between what you placed first and what you placed last — visible lines that are also weak lines. If you are set on bags, get help and run two mixers; otherwise price the truck.
Budget for the tools as well as the concrete: a mixer runs about $70/day, a plate compactor for the base about $80/day, and a concrete saw for the joints about $60/day.
What it would cost to hire out
A professionally installed basic slab runs roughly $4–$8 per square foot including labour, so for 120 sq ft:
| Route | Estimated total | What you spend |
|---|---|---|
| DIY | ≈ $439–$739 | Concrete, forms, base, reinforcement, tool rental — plus your weekend |
| Hire a contractor | ≈ $480–$960 | Everything, done to a finish, usually in a day |
The gap is labour, and it is real — but so is the risk transfer. A contractor who gets the finish wrong fixes it; if you do, you own it. See DIY vs hiring a pro and slab cost by size for the full breakdown of where each route makes sense.
Watch out on a slab this size
People size patios to the furniture and forget the chairs. Measure the table, then add 3 feet on every side a chair pulls out on. It is far cheaper to widen a form than to extend a slab later, and a poured-on extension never looks like it belongs.
The arithmetic
Volume = 10 × 12 × (4 ÷ 12) = 40 ft³, then ÷ 27 = 1.48 cubic yards. An 80 lb bag yields 0.60 ft³, so 40 ÷ 0.60 = 67 bags before waste; add 10% and round up to 74 bags. Ready-mix rounds up to the quarter yard, giving 1.75 yd³. Every constant behind those steps is documented in how we calculate, and the reasoning is in how much concrete do I need?
Other slab sizes
Last updated: 2026-08-21.
Bag yields from the
QUIKRETE #1101
data sheet. Joint spacing, panel aspect and cut depth follow standard residential
practice (2–3 × slab thickness, 1.5:1 max panel ratio, cut to ¼ depth). Cost
figures are US-national-average estimates and vary by region and supplier.
Planning estimates only — see terms.