How much concrete do you need for a 12×16 slab?

A 12×16 ft slab poured 4 inches thick needs 2.37 cubic yards (64 cu ft) of concrete. With 10% extra for waste, buy 118 bags of 80 lb premix or order 2.61 yards of ready-mix.

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Your results

Concrete to buy (incl. 10% extra)2.61 cu yd
80 lb bags118
60 lb bags157
40 lb bags235
Exact volume64 cu ft (2.37 cu yd)
How much concrete do you need for a 12×16 slab — diagram

Concrete for a 12×16 slab at different thicknesses

The slab covers 192 square feet. Every extra inch of thickness adds about 0.59 cubic yards. Quantities below include 10% for waste.

ThicknessCubic yards80 lb bags60 lb bags40 lb bags
3.5 in2.28103137206
4 in2.61118157235
5 in3.26147196294
6 in3.91176235352
8 in5.21235313470

Bags or ready-mix for this size?

At 2.61 cubic yards you are in the gray zone between bags and a truck. 118 bags of 80 lb weigh about 9,440 lb in total — get a ready-mix quote (ask about short-load fees) and compare it with the bag price before deciding.

How heavy is a 12×16 slab?

Normal-weight concrete weighs about 150 lb per cubic foot, so a 4-inch 12×16 slab weighs roughly 9,600 lb (4.8 tons) once cured. Make sure your base is compacted gravel on firm, undisturbed soil.

The math

12 ft × 16 ft × (4 in ÷ 12) = 64 cu ft 64 cu ft ÷ 27 = 2.37 cu yd +10% waste = 70.4 cu ft 70.4 ÷ 0.6 cu ft per 80 lb bag = 118 bags (rounded up)

Common questions

How many 80 lb bags of concrete for a 12x16 slab?

118 bags for a 4-inch slab including 10% extra (107 with no extra). At 6 inches thick you need 176 bags.

How many yards of concrete for a 12x16 slab 6 inches thick?

3.91 cubic yards including 10% extra, or 3.56 yards exactly.

How many 60 lb bags for a 12x16 slab?

157 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.

Similar sizes

10×12 slab10×16 slab10×20 slab12×12 slab12×20 slab12×24 slab14×14 slab16×16 slab

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