How Much Concrete for a 6x6 Slab? Yards & Bags

How Much Concrete for a 6 × 6 Slab?

A 6 × 6 ft slab is 36 sq ft. It needs 0.49 cubic yards of concrete at 4 inches thick or 0.73 yd³ at 6 inches, including 10% extra.

6 × 6 ft slab, 10% extra included
Order	4 in thick	6 in thick
Cubic yards	0.49	0.73
80-lb bags	22	33
60-lb bags	30	44
50-lb bags	36	53
40-lb bags	44	66
Cubic meters	0.37	0.56

A 6 × 6 ft pad suits a hot water heater enclosure, a small shed, a bench or a landing at the bottom of steps.

6 × 6 slab at other thicknesses

Concrete for a 6 × 6 ft slab
Thickness	yd³ exact	yd³ +10%	80-lb bags	60-lb bags
3.5 in	0.39	0.43	20	26
4 in	0.44	0.49	22	30
5 in	0.56	0.61	28	37
6 in	0.67	0.73	33	44
8 in	0.89	0.98	44	59

How it's worked out

6 × 6 = 36 sq ft · 36 × 4 ÷ 12 = 12.0 ft³ · ÷ 27 = 0.44 yd³ · × 1.10 = 0.49 yd³

For bags, the 13.2 ft³ (with extra) is divided by each bag's yield: 0.60 ft³ for 80 lb, 0.45 for 60 lb, 0.375 for 50 lb and 0.30 for 40 lb, then rounded up. At 4 inches the slab itself weighs about 1,700 lb, using the 140 lb/ft³ unit weight QUIKRETE lists for its Concrete Mix.

Bags or a truck?

At 0.49 yd³ (22 × 80-lb bags), bagged mix is the practical choice. A ready-mix truck for a load this small would usually carry a minimum-order or short-load charge.

Don't forget the base: most slabs sit on a compacted layer of gravel, and thicker edges or footings around the perimeter add concrete. Use the footing calculator for a thickened edge.

Frequently asked questions

How many yards of concrete for a 6x6 slab?

0.44 cubic yards at 4 inches thick and 0.67 yd³ at 6 inches, before waste. With 10% extra, order 0.49 or 0.73 yd³.

How many bags of concrete for a 6x6 slab?

At 4 inches with 10% extra: 22 bags of 80-lb mix, 30 of 60 lb, 36 of 50 lb or 44 of 40 lb. At 6 inches: 33 bags of 80 lb or 44 of 60 lb.

How many cubic feet of concrete for a 6x6 slab?

12.0 ft³ at 4 inches (36 sq ft × 4 ÷ 12) and 18.0 ft³ at 6 inches, before waste.

How thick should a 6x6 slab be?

Four inches is usual for patios, walkways and shed pads. Garage floors, driveways and pads for heavy loads are commonly 5 to 6 inches. Follow local code or your plans for anything structural.

Sources

QUIKRETE: Concrete Mix No. 1101 data sheet (Revised Oct 2022; checked Nov 11, 2026)