How Many Bags of Concrete for a 10x12 Slab?
A 10x12 concrete slab at 4 inches needs about 1.63 yd3 with 10% waste, or 74 80 lb bags. See 4, 5, 6 inch bag counts and cost checks.
A 10x12 concrete slab is 120 square feet. At 4 inches thick, it needs about 1.48 yd3 before waste, 1.63 yd3 with 10% waste, or about 74 common 80 lb bags. The same slab is about 98 60 lb bags or 147 40 lb bags.
Use the Concrete Bag Calculator for exact bag count, price, and waste. If the 10x12 slab is for a shed, also see the Shed Base Concrete Calculator Guide.
Competitor pages such as ConcreteCalculatorMax's slab calculator and ConcreteCalculator.pro's concrete slab calculator answer broad slab quantity intent. This page gives the direct 10x12 answer and then helps decide whether bags, ready-mix, or an installed quote makes sense.
Quick answer
For a 10 ft x 12 ft slab:
| Thickness | With 10% waste | 80 lb bags | 60 lb bags | 40 lb bags |
|---|---|---|---|---|
| 4 in | 1.63 yd3 | 74 | 98 | 147 |
| 5 in | 2.04 yd3 | 92 | 123 | 184 |
| 6 in | 2.44 yd3 | 110 | 147 | 220 |
These are planning counts using common yields of 0.60 ft3 for 80 lb bags, 0.45 ft3 for 60 lb bags, and 0.30 ft3 for 40 lb bags. Always confirm the yield printed on the bag you plan to buy.
Slab thickness, base prep, reinforcement, drainage, frost, anchors, and permits should be confirmed with a qualified local professional.
10x12 slab formula
cubic yards = 10 x 12 x thickness in / 12 / 27
At 4 inches:
10 x 12 x 4 / 12 / 27 = 1.48 yd3 before waste
1.48 x 1.10 = 1.63 yd3 with 10% waste
To convert yards to 80 lb bags:
bags = cubic yards x 27 / 0.60
1.63 x 27 / 0.60 = 73.35, round up to 74 bags
For a broader size chart, see Concrete Bags for 100 Square Feet and the Concrete Bag Coverage Chart.
Cost check for a 10x12 slab
Material-only bag cost depends on local shelf price. This table uses the 4 in slab bag counts and placeholder prices.
| Bag size | Bags | Example price | Material check |
|---|---|---|---|
| 80 lb | 74 | $6.50 | $481.00 |
| 60 lb | 98 | $5.25 | $514.50 |
| 40 lb | 147 | $4.25 | $624.75 |
| Ready-mix | 1.63 yd3 | $165/yd3 + $125 delivery | $393.95 |
This does not include mixer rental, labor, wheelbarrow time, delivery minimums, base gravel, forms, reinforcement, finish, cleanup, tax, or contractor markup.
Use the Ready-Mix vs Bags Calculator before buying dozens of bags. A 10x12 slab is often near the point where ready-mix deserves a serious quote.
What changes the bag count?
| Change | Effect |
|---|---|
| 5 in thickness | Adds about 18 more 80 lb bags than a 4 in slab. |
| 6 in thickness | Adds about 36 more 80 lb bags than a 4 in slab. |
| Uneven base | Low spots can consume extra concrete. |
| Thickened edge | Estimate the edge separately and add it to the slab volume. |
| Bag yield | Fast-setting or specialty mixes may yield differently. |
| Waste factor | 5% may work for tight forms; 10% is safer for planning. |
For base depth, see How Much Gravel Under a Concrete Slab. For thickness decisions, see the Concrete Slab Thickness Guide.
FAQ
How many 80 lb bags for a 10x12 slab at 4 inches?
Plan about 74 common 80 lb bags with 10% waste. Without waste, the math is about 67 bags, but most projects should not buy with zero buffer.
How many 60 lb bags for a 10x12 slab?
At 4 inches thick with 10% waste, plan about 98 common 60 lb bags.
How much ready-mix for a 10x12 slab?
At 4 inches thick, plan about 1.63 yd3 with 10% waste. Ask the supplier about minimum order size, short-load fees, delivery, and chute reach.
Is a 10x12 slab too big for bags?
It can be done with bags, but 74 80 lb bags is a lot of mixing. Compare ready-mix, rental mixer, labor, and schedule before deciding.
Should a 10x12 shed slab be 4 inches thick?
Four inches is a common planning starting point, but shed weight, stored equipment, soil, frost, base prep, and local requirements can change the design.
Next step
Run your exact inputs in the Concrete Bag Calculator, then compare material and installed bids in the Concrete Quote Reviewer. Contractors can prepare a client-facing scope with the Concrete Proposal Kit.
Quote planning next step
Turn this guide into a concrete buying check
Run the matching calculator, then compare ready-mix, bagged concrete, delivery fees, access needs, and quote gaps before you buy materials or approve a contractor number.