12 × 12 ft slab: the short answer
Poured 4 inches thick (with 10% waste), a 12 × 12 ft slab needs about 52.8 cubic feet of concrete — roughly 89 × 80 lb bags, or about 1.96 cubic yards of ready-mix.
Slab size
Concrete for a 12 × 12 ft slab
A 12 × 12 ft slab poured 4 inches thick needs about 52.8 cubic feet of concrete — roughly 89 × 80 lb bags, or 1.96 cubic yards of ready-mix (includes 10% waste). Change the thickness, bag size, or shape below.
Concrete needed
—Enter dimensions to estimate concrete.
| Bags (incl. waste) | — |
|---|---|
| Ready-mix (cubic yards) | — |
| Volume (cubic feet) | — |
| Estimated cost | — |
Shopping list
Run the calculator to prepare a list.
Estimate only.
Includes your waste allowance (concrete can't be reused). Bag yields are typical for standard
mixes; confirm on the bag. Past about 1 cubic yard, ready-mix delivery is usually cheaper and
easier than mixing bags.
Before you pour
Concrete can't be reused once mixed, so the 10% allowance matters. For anything structural, confirm thickness and reinforcement with your local code. Adjust thickness and bag size in the calculator for your exact pour.
Standard volume math at 4″ with 10% waste; 80 lb bag ≈ 0.6 cu ft. Estimates only.
What a 12 × 12 ft slab is usually used for
A 12 × 12 ft slab is a full patio or garden-room footprint: 144 sq ft and about 1.8 cubic yards of concrete at 4 inches. This is a job-sized pour that most people do with ready-mix and a small crew, and where planning the day matters more than the arithmetic.
How to decide
At this volume, ready-mix delivery is the realistic route, and the planning shifts to logistics: truck access, form height, finishing help, and curing. The calculator gives the volume including a 10% waste allowance; confirm your site's actual thickness, because a 5-inch slab adds about 25% to the volume.
Checks before you pour
- Confirm thickness with the slab's intended use before ordering the truck.
- Arrange finishing help; a 144 sq ft slab sets faster than one person can finish.
- Verify truck access and check for overhead wires or low branches on the route.
FAQ
How much concrete for a 12 × 12 ft slab?
At 4 inches thick with 10% waste, a 12 × 12 ft slab needs about 52.8 cubic feet — roughly 89 × 80 lb bags (or 118 × 60 lb), or 1.96 cubic yards of ready-mix.
Bags or ready-mix for a 12 × 12 ft slab?
At about 1.96 cubic yards, this slab is past the point where bags make sense — 89 bags is a lot of mixing. Ready-mix delivery is usually cheaper and lets you pour it all at once.
Sources & verification
Source links and page assumptions reviewed .
- QUIKRETE: quantity calculator — Manufacturer quantity calculator and bag-yield guidance for concrete mixes.
- QUIKRETE: concrete mix data sheet — States an 80 lb bag of concrete mix yields about 0.6 cu ft at recommended consistency.
Estimate only, based on standard volume math at 4″ thickness with 10% waste. Confirm bag yield on the package and consult a pro for structural work.