How Much Concrete for a 16×16 Slab?
Quick Answer
A 16×16 foot slab poured 4 inches thick needs 3.16 cubic yards of concrete. Order about 3.5 cubic yards to cover a 10% waste factor. At 256 square feet, ready-mix delivery is far more practical than mixing bags.
- 4-inch slab: 3.16 cubic yards (85 cubic feet)
- Order ~3.5 cubic yards with 10% waste
- Bag equivalent: ~142 80-lb bags or ~190 60-lb bags
- Ready-mix cost: $474–$553 delivered
Formula
Multiply length, width, and thickness (in feet) to get cubic feet, then divide by 27 to convert to cubic yards. For a 4-inch slab, thickness is 4 ÷ 12 = 0.333 ft.
Step-by-Step Calculation
- 1
Slab volume in cubic feet
16 × 16 × 0.333 = 85.3 cubic feet
- 2
Convert to cubic yards
85.3 ÷ 27 = 3.16 cubic yards
- 3
Add 10% waste
3.16 × 1.10 = 3.5 cubic yards
- 4
Bag equivalent (80-lb)
85.3 ÷ 0.6 cu ft per bag = 142 bags
16×16 Slab Concrete by Thickness
| Thickness | Cubic Feet | Cubic Yards | 80-lb Bags | Ready-Mix Cost* |
|---|---|---|---|---|
| 4 inches | 85 | 3.16 | 142 | $474–$553 |
| 5 inches | 107 | 3.95 | 178 | $593–$691 |
| 6 inches | 128 | 4.74 | 213 | $711–$830 |
*Ready-mix at $150–$175 per cubic yard delivered. A 256 sq ft pour is well past the point where bags make sense.
Frequently Asked Questions
How many bags of concrete for a 16×16 slab?
A 4-inch 16×16 slab needs about 142 80-lb bags or 190 60-lb bags. That is far too many to mix by hand — ready-mix delivery is cheaper and saves a full day of labor.
How thick should a 16×16 slab be?
Four inches suits patios, sheds, and seating areas. Step up to 5 or 6 inches for garages, workshops, or anything holding vehicles or heavy equipment. Always pour over 4 inches of compacted gravel.
How much does a 16×16 concrete slab cost?
Materials run $474–$830 depending on thickness. A professionally poured and finished 16×16 slab costs $1,536–$3,072 (about $6–$12 per sq ft) including labor, forms, and finishing.