Concrete Calculator: 10 × 12 ft slab
Work out cubic yards of concrete and how many 60 or 80 lb bags you need for a slab, with a waste allowance and rough cost.
// Bill of materials
Costs are rough, materials only — edit the price to match your quote.
Pre-filled for a 10 × 12 ft slab. Change any value to recalculate, or start from scratch.
How it's calculated
Volume = length × width × thickness. We convert thickness from inches to feet, add your waste allowance, then divide by the yield of one bag and round up. Cubic yards is the volume divided by 27.
Worked example — 10 × 12 ft slab
- Length
- 12 ft
- Width
- 10 ft
- Thickness
- 4 in
- Bag size
- 80 lb bag (0.60 cu ft)
- Waste / over-order
- 5 %
- Price per bag
- 5 $
Nearby sizes
| Room size | Bags to buy | |
|---|---|---|
| 8 × 8 ft slab | 38 bags | Open |
| 8 × 10 ft slab | 47 bags | Open |
| 10 × 10 ft slab | 59 bags | Open |
| 10 × 12 ft slab (this page) | 70 bags | |
| 10 × 16 ft slab | 94 bags | Open |
| 12 × 12 ft slab | 84 bags | Open |
| 12 × 16 ft slab | 112 bags | Open |
| 12 × 20 ft slab | 140 bags | Open |
| 16 × 16 ft slab | 150 bags | Open |
| 16 × 20 ft slab | 187 bags | Open |
| 16 × 24 ft slab | 224 bags | Open |
| 20 × 20 ft slab | 234 bags | Open |
Tips for buying concrete
- For anything over about half a cubic yard, price out ready-mix delivery — bags get expensive and slow fast.
- A standard 80 lb bag yields about 0.6 cubic feet; a 60 lb bag about 0.45. Always check the yield on the bag.
- Order 5–10% extra: subgrade is never perfectly flat, and running out mid-pour ruins the finish.
- Compact and dampen the base before you pour, and set your forms dead level — concrete won't fix a bad base.
- Have more hands and tools ready than you think; concrete gives you very little working time once it's mixed.
- For structural footings or columns, check local code for depth and rebar — this tool sizes volume, not structure.
Frequently asked questions
How many bags of concrete are in a cubic yard?
A cubic yard is 27 cubic feet. At 0.6 cu ft per 80 lb bag that's about 45 bags; at 0.45 cu ft per 60 lb bag, about 60 bags. That's why bags only make sense for small pours.
How thick should a concrete slab be?
4 inches is standard for patios and walkways; 5–6 inches for driveways or anything bearing vehicles. Enter your thickness and the calculator does the rest.
How much concrete do I need for a 10x10 slab?
A 10×10 slab at 4 inches is about 1.3 cubic yards. That's roughly 59 eighty-pound bags — at that size, ready-mix delivery is usually cheaper and easier.
Should I add extra for waste?
Yes. 5–10% covers spillage and an uneven base. It's far better to have a little left over than to stop a pour to buy more.