How much concrete do you need for a 16×16 slab?

A 16×16 ft slab poured 4 inches thick needs 3.16 cubic yards (85.3 cu ft) of concrete. With 10% extra for waste, buy 157 bags of 80 lb premix or order 3.48 yards of ready-mix.

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Your results

Concrete to buy (incl. 10% extra)3.48 cu yd
80 lb bags157
60 lb bags209
40 lb bags313
Exact volume85.33 cu ft (3.16 cu yd)
How much concrete do you need for a 16×16 slab — diagram

Concrete for a 16×16 slab at different thicknesses

The slab covers 256 square feet. Every extra inch of thickness adds about 0.79 cubic yards. Quantities below include 10% for waste.

ThicknessCubic yards80 lb bags60 lb bags40 lb bags
3.5 in3.04137183274
4 in3.48157209313
5 in4.35196261392
6 in5.21235313470
8 in6.95313418626

Bags or ready-mix for this size?

At 3.48 cubic yards, bags mean mixing 157 bags weighing roughly 6.3 tons. Ready-mix delivery is usually the practical choice at this size, and it gives a more consistent slab.

How heavy is a 16×16 slab?

Normal-weight concrete weighs about 150 lb per cubic foot, so a 4-inch 16×16 slab weighs roughly 12,800 lb (6.4 tons) once cured. Make sure your base is compacted gravel on firm, undisturbed soil.

The math

16 ft × 16 ft × (4 in ÷ 12) = 85.33 cu ft 85.33 cu ft ÷ 27 = 3.16 cu yd +10% waste = 93.87 cu ft 93.87 ÷ 0.6 cu ft per 80 lb bag = 157 bags (rounded up)

Common questions

How many 80 lb bags of concrete for a 16x16 slab?

157 bags for a 4-inch slab including 10% extra (143 with no extra). At 6 inches thick you need 235 bags.

How many yards of concrete for a 16x16 slab 6 inches thick?

5.21 cubic yards including 10% extra, or 4.74 yards exactly.

How many 60 lb bags for a 16x16 slab?

209 bags of 60 lb concrete for a 4-inch slab with 10% extra.

Want the full method, tips and other sizes? See the concrete calculator guide.

Last reviewed November 1, 2026. Results are estimates — confirm with your supplier.

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