How much concrete do you need for a 24×30 slab?

A 24×30 ft slab poured 4 inches thick needs 8.89 cubic yards (240 cu ft) of concrete. With 10% extra for waste, buy 440 bags of 80 lb premix or order 9.78 yards of ready-mix.

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Your results

Concrete to buy (incl. 10% extra)9.78 cu yd
80 lb bags440
60 lb bags587
40 lb bags880
Exact volume240 cu ft (8.89 cu yd)
How much concrete do you need for a 24×30 slab — diagram

Concrete for a 24×30 slab at different thicknesses

The slab covers 720 square feet. Every extra inch of thickness adds about 2.22 cubic yards. Quantities below include 10% for waste.

ThicknessCubic yards80 lb bags60 lb bags40 lb bags
3.5 in8.56385514770
4 in9.78440587880
5 in12.225507341,100
6 in14.676608801,320
8 in19.568801,1741,760

Bags or ready-mix for this size?

At 9.78 cubic yards, bags mean mixing 440 bags weighing roughly 17.6 tons. Ready-mix delivery is usually the practical choice at this size, and it gives a more consistent slab.

How heavy is a 24×30 slab?

Normal-weight concrete weighs about 150 lb per cubic foot, so a 4-inch 24×30 slab weighs roughly 36,000 lb (18 tons) once cured. Make sure your base is compacted gravel on firm, undisturbed soil.

The math

24 ft × 30 ft × (4 in ÷ 12) = 240 cu ft 240 cu ft ÷ 27 = 8.889 cu yd +10% waste = 264 cu ft 264 ÷ 0.6 cu ft per 80 lb bag = 440 bags (rounded up)

Common questions

How many 80 lb bags of concrete for a 24x30 slab?

440 bags for a 4-inch slab including 10% extra (400 with no extra). At 6 inches thick you need 660 bags.

How many yards of concrete for a 24x30 slab 6 inches thick?

14.67 cubic yards including 10% extra, or 13.33 yards exactly.

How many 60 lb bags for a 24x30 slab?

587 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

20×20 slab20×24 slab20×30 slab24×24 slab30×30 slab30×40 slab40×40 slab

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