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How many 80 lb bags of concrete for a 10x10 slab 4 inches thick?

By the YardBrick Editorial Team · Last updated October 5, 2026

A 10x10 slab 4 inches thick needs 56 bags of 80 lb concrete before any waste allowance (75 bags if you buy 60 lb).

Check it with your own numbers

Open the Concrete Calculator with these values

Length	10 ft
Width	10 ft
Thickness	4 in
Extra for waste	0 %
Concrete needed	1.23 yd³
Cubic feet	33.3 ft³
80 lb bags	56
60 lb bags	75

The bag math

The slab holds 33.3 cubic feet. One 80 lb bag of premix yields about 0.6 ft³ once mixed, so 33.3 ÷ 0.6 rounds up to 56 bags. A 60 lb bag yields 0.45 ft³, which is 75 bags. Those numbers assume a perfectly flat base and zero spillage, which does not happen.

How many to actually buy

Add 10% and the count goes to 62 bags of 80 lb. Most home centers take back unopened bags, so buying a few over beats a half-hour round trip with wet concrete curing in the forms. At about 3,500 lb of material, plan on two trips in a half-ton pickup or pay for delivery.

Mixing 56+ bags in one day

This is where most DIY slabs go wrong. If the first section starts to set before the last section is placed, you get a cold joint and a weak line through the pad. A few ways to keep up:

Rent a towable 9 ft³ mixer. It handles 4 to 5 bags per batch, so you are down to about 13 batches.
Have one person mixing, one wheeling and one screeding.
Start early on a cool, cloudy day. Hot sun and wind cut your working time in half.
Pre-stage the bags next to the mixer in rows of four before you start.

Is a truck cheaper?

The same slab is 1.23 yd³ of ready-mix with no waste. Even with a short-load fee, a truck often costs about the same as 62 bags once you price in a mixer rental and the extra labor. Bags make the most sense when the truck cannot reach the site and you would be wheeling ready-mix 100 ft anyway.

Bag strength

Standard bagged mixes are rated around 4,000 psi. For a slab that will carry a vehicle or a heavy hot tub, look for a 5,000 psi high-strength mix. The yield per bag is the same.