How much concrete for a 8 × 8 slab?
A 8 × 8 ft slab (64 sq ft) poured 4 inches thick takes 0.79 cubic yards of concrete. With 10% extra for uneven ground and spillage, order 0.87 cubic yards of ready-mix or buy 40 bags of 80 lb mix.
| Thickness | Exact volume | Order (+10%) | 80 lb bags | 60 lb bags | Typical use |
|---|---|---|---|---|---|
| 4 in | 0.79 yd³ | 0.87 yd³ (0.66 m³) | 40 | 53 | Patio, walkway, shed floor |
| 5 in | 0.99 yd³ | 1.09 yd³ (0.83 m³) | 49 | 66 | Hot tub pad, light driveway |
| 6 in | 1.19 yd³ | 1.3 yd³ (1 m³) | 59 | 79 | 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
23.5 cubic feet = 0.87 cubic yards = 0.66 m³. Above about 1 cubic yard, ready-mix delivery is usually cheaper and faster than bags.
Rough material cost (cheapest option)
$148Ready-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 8x8 slab?
At 4 inches thick, 40 bags of 80 lb concrete mix or 53 bags of 60 lb mix, including 10% extra. At 6 inches, 59 bags of 80 lb mix.
Should I use bags or ready-mix for a 8x8 slab?
Bags. At 0.87 cubic yards the job is small enough to mix by hand or with a rented mixer, and ready-mix suppliers charge a short-load fee for small orders.
How do you calculate concrete for a 8 by 8 slab?
Multiply length × width × thickness in feet: 8 × 8 × (4 ÷ 12) = 21.3 cubic feet. Divide by 27 to get 0.79 cubic yards, then add 5–10% extra.