What a 24x24 slab is for
A 24x24 slab is the classic roomy two-car garage: two cars or pickups with space to open doors and a strip along the walls for shelves and a bench. It also suits a large workshop or a pole barn.
Concrete for a 24x24 slab at 4, 5 and 6 inches
Every inch of thickness on a 24x24 slab is 48 cubic feet, or 1.78 cubic yards. The ready mix order and the bags in this table include 10 percent extra. Change the thickness or the extra in the calculator above.
| Thickness | Cubic feet | Cubic yards | Ready mix to order | 80 lb bags | 60 lb bags |
|---|---|---|---|---|---|
| 4 in | 192 | 7.11 | 7.82 cu yd | 352 | 470 |
| 5 in | 240 | 8.89 | 9.78 cu yd | 440 | 587 |
| 6 in | 288 | 10.67 | 11.73 cu yd | 528 | 704 |
The 4 inch row by hand: 24 × 24 × 0.333 = 192 cubic feet, and 192 ÷ 27 = 7.11 cubic yards. With 10 percent extra that is 211.2 cubic feet. An 80 lb bag makes 0.60 cubic feet and a 60 lb bag makes 0.45, so it takes 352 of one or 470 of the other.
Quikrete says a sidewalk should be at least 4 inches thick and small slabs normally run 4 to 6 inches, depending on the load. The concrete slab calculator page covers what the building code asks for.
Bags or a truck for a 24x24 slab
From bags, it is 352 bags of 80 lb mix at 4 inches, 28,160 lb to lift and mix, about $2,003 at McCoy's price of $5.99 a bag, or $5.69 for 42 or more.
From a truck, it is 7.82 cubic yards, about $860 to $1,173 at HomeAdvisor's $110 to $150 per cubic yard delivered. The National Ready Mixed Concrete Association says a truck mixer carries 8 to 12 cubic yards, so this is less than one truck load. HomeAdvisor says an order under a full truckload can carry a short-load fee of $40 to $60 per cubic yard, and suppliers often have a minimum order.
By these prices a 24x24 slab costs about $830 to $1,143 less from a truck than from bags, and it saves lifting 28,160 lb of mix. A short-load fee or a minimum order comes out of that gap, so get a delivered price for 7.82 cubic yards and compare it with $2,003. It is a bag job only if that quote comes in higher or a truck cannot reach the slab. The association notes that a loaded truck weighs about 80,000 lb and may not be able to cross loose dirt or a residential curb.
| Thickness | 80 lb bags | Bags weigh | Bags cost | Ready mix | Ready mix cost |
|---|---|---|---|---|---|
| 4 in | 352 | 28,160 lb | $2,003 | 7.82 cu yd, less than one truck load | $860 to $1,173 |
| 5 in | 440 | 35,200 lb | $2,504 | 9.78 cu yd, about one truck load | $1,076 to $1,467 |
| 6 in | 528 | 42,240 lb | $3,004 | 11.73 cu yd, about one truck load | $1,290 to $1,760 |
Prices are from the sources below, checked in October 2026; multiply the table by your own to compare. Gravel, steel, forms, finishing and labor are extra.
Pouring a 24x24 slab
At 4 inches, 7.82 cubic yards, just under the 8 cubic yards NRMCA gives as the small end of a truck. At 5 inches the order is 9.78 cubic yards and at 6 inches 11.73, both one full truck. Plan the pour in strips: form or set a screed rail every 10 or 12 feet, place and strike off one strip at a time, and start floating the first strip while the next one is placed.
Gravel base and slope
A 4 inch gravel base under a 24x24 slab is 192 cubic feet, or 7.11 cubic yards. Quikrete says to spread and compact 3 to 4 inches, and a 3 inch base is 144 cubic feet, or 5.33 cubic yards. Those are volumes of the finished layer. Gravel settles when it is compacted, so order a little more.
Outside, Quikrete says to slope the slab away from buildings and gives 1/4 inch per foot as the usual fall. Either way across a 24x24 slab, that is 6 inches from one edge to the other. Set the forms to the slope, and the screed follows them.
As a garage floor
Dubuque, Iowa, publishes a simple foundation for a detached garage of up to 720 square feet: a floor at least 4 inches thick on a grade beam, a thickened edge at least 12 inches deep and 12 inches wide under every wall, with 6x6 welded wire or #4 bars no more than 2 feet apart both ways. A 24x24 garage is 576 square feet. Your town may want something else, especially where the ground freezes deep, so take this as an example and ask first.
The grade beam is the outer foot of the slab, made 8 inches deeper than the floor. Around a 24x24 slab that is 92 square feet of edge, 61.3 cubic feet, or 2.27 cubic yards more concrete. With 10 percent extra, that adds 2.5 cubic yards, for an order of about 10.32 at 4 inches. Dig the edge deeper if the grade falls away, because Dubuque measures the 12 inches from the ground outside.
Rebar or wire mesh
With bars 24 inches on center both ways, held 3 inches back from each edge, a 24x24 slab takes 13 bars each way, all 23 feet 6 inches long. That is 611 feet of bar. With 10 percent extra, buy 34 bars 20 feet long. Every bar is longer than the 20 foot length sold, so each one is made of pieces that overlap. Fridley, Minnesota, says to overlap joined bars by at least 40 bar diameters, which is 20 inches for a 1/2 inch #4 bar. The 10 percent extra is there for those overlaps and the offcuts.
With wire mesh instead, 8 sheets 8 feet by 12.5 feet, lapped 8 inches, cover it. The spacing and the sheet size are where the calculator starts. Your plans or your building department set the steel for your slab.
Control joints
Quikrete says control joints in a 4 inch slab go every 6 to 8 feet and about a quarter of the slab deep, which is 1 inch. Keeping them no more than 8 feet apart cuts a 24x24 slab into 3 panels each way. That makes 9 panels, each 8 feet square, with 96 feet of joint to cut.
Before you pour a 24x24 slab
Mark the door opening on the forms before the pour. The wall plates stop at the opening, and Dubuque asks for a 1/2 inch anchor bolt within 12 inches of each end of each plate, so the bolts beside the door have to go in the right spot while the concrete is wet. Between those, the handout spaces bolts no more than 6 feet apart, set at least 7 inches into the concrete.
Other slab sizes
8x1010x1010x1212x1210x2012x2016x2020x2020x2424x2424x3030x40
Common questions
How much concrete do I need for a 24x24 slab?
A 24 by 24 foot slab 4 inches thick holds 192 cubic feet of concrete, which is 7.11 cubic yards. With 10 percent extra, order 7.82 cubic yards of ready mix. At 5 inches thick it holds 8.89 cubic yards and at 6 inches 10.67.
How many 80 lb bags of concrete do I need for a 24x24 slab?
352 bags at 4 inches thick, with 10 percent extra. They weigh 28,160 lb in all and cost about $2,003 at the store price checked in October 2026. At 5 inches thick it is 440 bags and at 6 inches 528.
How thick should a 24x24 concrete slab be?
Quikrete calls for at least 4 inches for a sidewalk and 4 to 6 inches for small slabs, depending on the load. The International Residential Code minimum for a house floor slab is 3.5 inches. On a 24x24 slab each extra inch adds 1.78 cubic yards, so going from 4 to 6 inches takes the ready mix order from 7.82 to 11.73 cubic yards. Ask your building department what it wants for a driveway or a garage floor.
Does a 24x24 garage slab need air-entrained concrete?
Where winters freeze, yes. NRMCA says air-entrained concrete is required for concrete exposed to freezing, and a garage floor also takes road salt off the cars. Tell the plant how the slab will be used when you order.
How many truck loads for a 24x24 slab?
One. NRMCA says a truck mixer carries 8 to 12 cubic yards, and a 24x24 slab is under 12 cubic yards to order even at 6 inches thick, unless you add a thickened edge.
How much concrete for a 24x24 garage slab with a thickened edge?
About 10.32 cubic yards with 10 percent extra: 7.82 for the 4 inch floor and 2.5 for a grade beam 12 inches deep and 12 inches wide around the edge, the kind Dubuque, Iowa, allows for a detached garage of up to 720 square feet.
Tools for this job
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- Form stakes. Hold the form boards in place while you pour.
- Concrete float. Smooths the surface after the concrete is leveled.
- Edger. Rounds the slab edges so they do not chip.
- Groover. Cuts control joints so cracks follow a straight line.
- Finishing trowel. Gives the slab its final smooth surface.
- Rubber boots. Keep wet concrete off your skin while you stand in the pour.
Sources
- Quikrete, Pouring and Finishing Concrete Slabs
- Quikrete, Concrete Sidewalks and Small Slabs project guide
- Quikrete Concrete Mix data sheet (yield per bag)
- National Ready Mixed Concrete Association, CIP 31: Ordering Ready Mixed Concrete
- International Residential Code 2021, Chapter 5: concrete floors on the ground (R506)
- International Residential Code 2021, Chapter 4: foundations (R403, concrete cover over steel)
- Wire Reinforcement Institute, Manual of Standard Practice: Structural Welded Wire Reinforcement
- City of Dubuque, Iowa, minimum requirements for a detached garage slab
- City of Fridley, Minnesota, Garage Slabs handout
- PJ's Rebar, stock rebar sizes and lengths
- International Residential Code 2021, Chapter 1: work exempt from permit (R105.2)
- McCoy's Building Supply: Quikrete Concrete Mix, 80 lb bag
- HomeAdvisor: concrete delivery cost, per cubic yard and short-load fees
Facts on this page were last checked against these sources in October 2026.