How much concrete for a 10 × 20 slab?
A 10 × 20 ft slab (200 sq ft) poured 4 inches thick takes 2.47 cubic yards of concrete. With 10% extra for uneven ground and spillage, order 2.72 cubic yards of ready-mix or buy 123 bags of 80 lb mix.
| Thickness | Exact volume | Order (+10%) | 80 lb bags | 60 lb bags | Typical use |
|---|---|---|---|---|---|
| 4 in | 2.47 yd³ | 2.72 yd³ (2.08 m³) | 123 | 163 | Patio, walkway, shed floor |
| 5 in | 3.09 yd³ | 3.4 yd³ (2.6 m³) | 153 | 204 | Hot tub pad, light driveway |
| 6 in | 3.7 yd³ | 4.07 yd³ (3.11 m³) | 184 | 245 | 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
73.3 cubic feet = 2.72 cubic yards = 2.08 m³. Above about 1 cubic yard, ready-mix delivery is usually cheaper and faster than bags.
Rough material cost (cheapest option)
$462Ready-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 10x20 slab?
At 4 inches thick, 123 bags of 80 lb concrete mix or 163 bags of 60 lb mix, including 10% extra. At 6 inches, 184 bags of 80 lb mix.
Should I use bags or ready-mix for a 10x20 slab?
Ready-mix is usually cheaper and much less work above about 1 cubic yard, and this slab needs 2.72. Under 4–5 yards many suppliers add a short-load fee, so compare a quote with 123 bags.
How do you calculate concrete for a 10 by 20 slab?
Multiply length × width × thickness in feet: 10 × 20 × (4 ÷ 12) = 66.7 cubic feet. Divide by 27 to get 2.47 cubic yards, then add 5–10% extra.