How much concrete for a 24 × 36 slab?
A 24 × 36 ft slab (864 sq ft) poured 4 inches thick takes 10.67 cubic yards of concrete. With 10% extra for uneven ground and spillage, order 11.73 cubic yards of ready-mix or buy 528 bags of 80 lb mix.
| Thickness | Exact volume | Order (+10%) | 80 lb bags | 60 lb bags | Typical use |
|---|---|---|---|---|---|
| 4 in | 10.67 yd³ | 11.73 yd³ (8.97 m³) | 528 | 704 | Patio, walkway, shed floor |
| 5 in | 13.33 yd³ | 14.67 yd³ (11.21 m³) | 660 | 880 | Hot tub pad, light driveway |
| 6 in | 16 yd³ | 17.6 yd³ (13.46 m³) | 792 | 1056 | 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
316.8 cubic feet = 11.73 cubic yards = 8.97 m³. Above about 1 cubic yard, ready-mix delivery is usually cheaper and faster than bags.
Rough material cost (cheapest option)
$1,995Ready-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 24x36 slab?
At 4 inches thick, 528 bags of 80 lb concrete mix or 704 bags of 60 lb mix, including 10% extra. At 6 inches, 792 bags of 80 lb mix.
Should I use bags or ready-mix for a 24x36 slab?
Ready-mix is usually cheaper and much less work above about 1 cubic yard, and this slab needs 11.73. Under 4–5 yards many suppliers add a short-load fee, so compare a quote with 528 bags.
How do you calculate concrete for a 24 by 36 slab?
Multiply length × width × thickness in feet: 24 × 36 × (4 ÷ 12) = 288 cubic feet. Divide by 27 to get 10.67 cubic yards, then add 5–10% extra.