How much concrete for a 8 × 12 slab?
A 8 × 12 ft slab (96 sq ft) poured 4 inches thick takes 1.19 cubic yards of concrete. With 10% extra for uneven ground and spillage, order 1.3 cubic yards of ready-mix or buy 59 bags of 80 lb mix.
| Thickness | Exact volume | Order (+10%) | 80 lb bags | 60 lb bags | Typical use |
|---|---|---|---|---|---|
| 4 in | 1.19 yd³ | 1.3 yd³ (1 m³) | 59 | 79 | Patio, walkway, shed floor |
| 5 in | 1.48 yd³ | 1.63 yd³ (1.25 m³) | 74 | 98 | Hot tub pad, light driveway |
| 6 in | 1.78 yd³ | 1.96 yd³ (1.5 m³) | 88 | 118 | 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
35.2 cubic feet = 1.3 cubic yards = 1 m³. Above about 1 cubic yard, ready-mix delivery is usually cheaper and faster than bags.
Rough material cost (cheapest option)
$222Ready-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 8x12 slab?
At 4 inches thick, 59 bags of 80 lb concrete mix or 79 bags of 60 lb mix, including 10% extra. At 6 inches, 88 bags of 80 lb mix.
Should I use bags or ready-mix for a 8x12 slab?
Ready-mix is usually cheaper and much less work above about 1 cubic yard, and this slab needs 1.3. Under 4–5 yards many suppliers add a short-load fee, so compare a quote with 59 bags.
How do you calculate concrete for a 8 by 12 slab?
Multiply length × width × thickness in feet: 8 × 12 × (4 ÷ 12) = 32 cubic feet. Divide by 27 to get 1.19 cubic yards, then add 5–10% extra.