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

Change the numbers

The calculator below is pre-filled for this project. Adjust any value — including feet and inches — and the results update instantly.

Tip: enter feet and inches in separate boxes, or use decimals (10 ft 6 in = 10.5 ft).

Your results

Concrete to buy (incl. 10% extra)0.49 cu yd

80 lb bags22

60 lb bags30

40 lb bags44

Exact volume12 cu ft (0.44 cu yd)

How much concrete do you need for a 6×6 slab — diagram

Concrete for a 6×6 slab at different thicknesses

The slab covers 36 square feet. Every extra inch of thickness adds about 0.11 cubic yards. Quantities below include 10% for waste.

Thickness	Cubic yards	80 lb bags	60 lb bags	40 lb bags
3.5 in	0.43	20	26	39
4 in	0.49	22	30	44
5 in	0.61	28	37	55
6 in	0.73	33	44	66
8 in	0.98	44	59	88

Bags or ready-mix for this size?

At 0.49 cubic yards, this is a comfortable bag job. A rented drum mixer (or a mixing tub and a hoe for smaller pours) handles it in a few hours.

How heavy is a 6×6 slab?

Normal-weight concrete weighs about 150 lb per cubic foot, so a 4-inch 6×6 slab weighs roughly 1,800 lb (0.9 tons) once cured. Make sure your base is compacted gravel on firm, undisturbed soil.

The math

6 ft × 6 ft × (4 in ÷ 12) = 12 cu ft 12 cu ft ÷ 27 = 0.444 cu yd +10% waste = 13.2 cu ft 13.2 ÷ 0.6 cu ft per 80 lb bag = 22 bags (rounded up)

Common questions

How many 80 lb bags of concrete for a 6x6 slab?

22 bags for a 4-inch slab including 10% extra (20 with no extra). At 6 inches thick you need 33 bags.

How many yards of concrete for a 6x6 slab 6 inches thick?

0.73 cubic yards including 10% extra, or 0.67 yards exactly.

How many 60 lb bags for a 6x6 slab?

30 bags of 60 lb concrete for a 4-inch slab with 10% extra.

Want the full method, tips and other sizes? See the concrete calculator guide.

Last reviewed November 1, 2026. Results are estimates — confirm with your supplier.

How much concrete do you need for a 6×6 slab?