How much concrete for a 30 × 30 slab?
A 30 × 30 ft slab (900 sq ft) poured 4 inches thick takes 11.11 cubic yards of concrete. With 10% extra for uneven ground and spillage, order 12.22 cubic yards of ready-mix or buy 550 bags of 80 lb mix.
| Thickness | Exact volume | Order (+10%) | 80 lb bags | 60 lb bags | Typical use |
|---|---|---|---|---|---|
| 4 in | 11.11 yd³ | 12.22 yd³ (9.34 m³) | 550 | 734 | Patio, walkway, shed floor |
| 5 in | 13.89 yd³ | 15.28 yd³ (11.68 m³) | 688 | 917 | Hot tub pad, light driveway |
| 6 in | 16.67 yd³ | 18.33 yd³ (14.02 m³) | 825 | 1100 | Driveway, garage floor |
Bag counts include the 10% extra and assume 0.60 ft³ per 80 lb bag and 0.45 ft³ per 60 lb bag.
Change the size, thickness or price
330 cubic feet = 12.22 cubic yards = 9.34 m³. Above about 1 cubic yard, ready-mix delivery is usually cheaper and faster than bags.
Rough material cost (cheapest option)
$2,078Ready-mix often has a short-load fee under 4–5 yd³. Rough 2026 US prices, edit to match local quotes.
FAQ
How many bags of concrete for a 30x30 slab?
At 4 inches thick, 550 bags of 80 lb concrete mix or 734 bags of 60 lb mix, including 10% extra. At 6 inches, 825 bags of 80 lb mix.
Should I use bags or ready-mix for a 30x30 slab?
Ready-mix is usually cheaper and much less work above about 1 cubic yard, and this slab needs 12.22. Under 4–5 yards many suppliers add a short-load fee, so compare a quote with 550 bags.
How do you calculate concrete for a 30 by 30 slab?
Multiply length × width × thickness in feet: 30 × 30 × (4 ÷ 12) = 300 cubic feet. Divide by 27 to get 11.11 cubic yards, then add 5–10% extra.