How many cinder blocks do I need for a 24x24 garage?

70 blocks per course around the 96 ft perimeter (less a block at each corner) and 12 courses for 8 ft walls is 840 blocks; the 151 sq ft of door, entry and window openings take off 169, leaving 671, or 705 with 5% waste. A 12 x 20 ft one-car garage is 471 blocks, a 32 x 24 ft three-car 782.

How much does a cinder block garage cost per square foot?

Materials for reinforced walls and a 4 in slab come to $7.16 per square foot of floor on the 24 x 24 ft garage, $10.66 on the 12 x 20 ft and $6.29 on the 32 x 24 ft: small garages cost more per foot because the walls are long for the floor they enclose. Installed, HomeGuide's 2026 range for a block wall is $15 to $30 per square foot of wall with the footing and rebar, which on the 617 sq ft of wall in the 24 x 24 ft garage is $9,255 to $18,510 for the walls alone.

Do the cells of a garage wall need to be filled?

A wall holding up a roof is reinforced masonry under the residential code: vertical bars in grouted cells at the spacing the code or your engineer sets, a bond beam at the top and dowels into the footing. At a bar every 32 in the 24 x 24 ft garage takes 89 bags of 80 lb grout (1.97 cubic yards) and 36 vertical bars; at 48 in it is 69 bags and 25 bars, $140 less in grout. Either way the grout is a short load from the plant, not 89 bags mixed by hand; the cell fill guide has the break-even.

What if the walls are 10 ft instead of 8?

Two more courses on every wall: the 24 x 24 ft garage goes from 705 to 926 blocks, 57 to 75 bags of mortar and 89 to 111 bags of grout, $2,927 to $3,805 in wall materials. The taller wall may also need bars closer together; check the bar schedule before ordering.

How much concrete for the garage slab?

8 cubic yards for the 24 x 24 ft floor at 4 in with 10% waste, $1,200 delivered at $150 a yard; the 12 x 20 ft floor is 3.5 yards and pays the $75 short-load fee, $600 in all (147 bags of 80 lb, which is why nobody uses bags). Most garage floors are poured 5 in with a thickened edge; the garage floor guide has those volumes.

What is not in these figures?

The footing (sized by the code or an engineer for a building, not by the garden-wall rule), the rebar itself, the roof, the doors and windows, lintels over the openings, anchor bolts, stucco or paint, the permit and the labor. HomeGuide's $5 to $10 per block to lay is $3,355 to $6,710 on the 24 x 24 ft garage's 671 blocks.

How much does a cinder block garage cost? (blocks, mortar, grout and slab for 1, 2 and 3 car)

A 24 x 24 ft two-car garage with 8 ft walls of standard 8 x 8 x 16 in block is 705 blocks with 5% waste once the 16 x 7 ft door, the entry door and two windows are taken off, 57 bags of mortar and about $2,304 in materials with the cells empty; with a bar every 32 in and a bond beam it is $2,927, and the 4 in slab adds $1,200 of ready-mix, so about $4,127 for walls and floor before the footing, roof, doors and labor ($7.16 per square foot of floor). A one-car 12 x 20 ft garage is $2,559 on the same basis, a three-car 32 x 24 ft $4,829. The tables give blocks, mortar, grout and the slab for seven sizes at 2026 shelf prices you can change in the calculator.

Open the concrete block calculator

Blocks and mortar for the walls

Four walls 8 ft high (12 courses) of standard 8 x 8 x 16 in block at $2.50 with 5% waste, counted around the outside perimeter less one block at each corner, the garage door, a 3 x 7 ft entry door and 3 x 3 ft windows taken off as whole blocks. Mortar is 80 lb bags at $9.50, 13 blocks per bag plus 10%. Cells empty. Change any of it in the concrete block calculator.

Blocks and mortar, cells empty, 8 ft walls
Garage	Garage door, windows	Per course	Blocks	Mortar bags	Materials
12 x 20 ft (1 car)	one 9 x 7 ft, 1 window	46	471	38	$1,539
14 x 24 ft (1 car, deep)	one 9 x 7 ft, 1 window	55	584	48	$1,916
20 x 20 ft (2 car)	one 16 x 7 ft, 2 windows	58	554	45	$1,813
24 x 24 ft (2 car)	one 16 x 7 ft, 2 windows	70	705	57	$2,304
24 x 30 ft (2 car, deep)	one 16 x 7 ft, 2 windows	79	818	66	$2,672
32 x 24 ft (3 car)	16 x 7 and 9 x 7 ft, 2 windows	82	782	63	$2,554
36 x 24 ft (3 car, deep)	16 x 7 and 9 x 7 ft, 2 windows	88	857	70	$2,808

Reinforced walls: grout and bars

The same walls with a vertical bar every 32 in in a grouted cell, a bond beam course on top with two horizontal bars, grout in 80 lb bags of concrete at $7.00 plus 10% for spills. The bars are counted, not priced. Where the bar schedule allows 48 in, the 24 x 24 ft garage takes 69 bags of grout and 25 bars instead of 89 and 36.

Bars every 32 in, bond beam on top
Garage	Blocks	Mortar bags	Grout bags	Vertical bars	Materials
12 x 20 ft	471	38	60	24	$1,959
14 x 24 ft	584	48	73	29	$2,427
20 x 20 ft	554	45	71	30	$2,310
24 x 24 ft	705	57	89	36	$2,927
24 x 30 ft	818	66	103	41	$3,393
32 x 24 ft	782	63	100	42	$3,254
36 x 24 ft	857	70	109	45	$3,571

89 bags of grout is 1.97 cubic yards: order it as a short load with the slab or from the plant, and see the cell fill guide for the grout at every bar spacing.

The slab, and the building total

A 4 in slab the size of the garage with 10% waste, ready-mix at $150 a yard in quarter-yard steps and a $75 short-load fee under 5 yards, from the concrete cost calculator. The total is reinforced walls plus slab, and the last column divides it by the floor area. Footing, roof and openings are extra.

4 in slab at $150 per yard, walls reinforced
Garage	Slab (cu yd)	Slab	Walls	Walls + slab	Per sq ft floor
12 x 20 ft	3.5	$600	$1,959	$2,559	$10.66
14 x 24 ft	4.75	$788	$2,427	$3,215	$9.57
20 x 20 ft	5.5	$825	$2,310	$3,135	$7.84
24 x 24 ft	8	$1,200	$2,927	$4,127	$7.16
24 x 30 ft	10	$1,500	$3,393	$4,893	$6.80
32 x 24 ft	10.5	$1,575	$3,254	$4,829	$6.29
36 x 24 ft	11.75	$1,763	$3,571	$5,333	$6.17

Where the rest of the money goes

Labor: HomeGuide's $5 to $10 per block to lay is $3,355 to $6,710 on the 24 x 24 ft garage, more than the blocks themselves. The block wall cost guide has HomeGuide's full installed ranges per block, per square foot and per linear foot.
The footing is a continuous strip under all four walls, sized for the roof load and the frost line by the code or an engineer; price the concrete in the concrete cost calculator once you have the section. The block wall guide has the order of the work: footing, corners, courses, bars, grout, bond beam.
Openings need lintels: precast concrete or a lintel block with bars over each door and window, sized for the span. The 16 ft door opening is the big one.
Half blocks for the running bond at the corners and jambs, corner blocks, anchor bolts in the bond beam for the top plate, and the saw rental for the cuts.
A garage this size is a permit and an inspection of the footing, the bars and the grout before the roof goes on.

Frequently asked questions

How many cinder blocks do I need for a 24x24 garage?: 70 blocks per course around the 96 ft perimeter (less a block at each corner) and 12 courses for 8 ft walls is 840 blocks; the 151 sq ft of door, entry and window openings take off 169, leaving 671, or 705 with 5% waste. A 12 x 20 ft one-car garage is 471 blocks, a 32 x 24 ft three-car 782.
How much does a cinder block garage cost per square foot?: Materials for reinforced walls and a 4 in slab come to $7.16 per square foot of floor on the 24 x 24 ft garage, $10.66 on the 12 x 20 ft and $6.29 on the 32 x 24 ft: small garages cost more per foot because the walls are long for the floor they enclose. Installed, HomeGuide's 2026 range for a block wall is $15 to $30 per square foot of wall with the footing and rebar, which on the 617 sq ft of wall in the 24 x 24 ft garage is $9,255 to $18,510 for the walls alone.
Do the cells of a garage wall need to be filled?: A wall holding up a roof is reinforced masonry under the residential code: vertical bars in grouted cells at the spacing the code or your engineer sets, a bond beam at the top and dowels into the footing. At a bar every 32 in the 24 x 24 ft garage takes 89 bags of 80 lb grout (1.97 cubic yards) and 36 vertical bars; at 48 in it is 69 bags and 25 bars, $140 less in grout. Either way the grout is a short load from the plant, not 89 bags mixed by hand; the cell fill guide has the break-even.
What if the walls are 10 ft instead of 8?: Two more courses on every wall: the 24 x 24 ft garage goes from 705 to 926 blocks, 57 to 75 bags of mortar and 89 to 111 bags of grout, $2,927 to $3,805 in wall materials. The taller wall may also need bars closer together; check the bar schedule before ordering.
How much concrete for the garage slab?: 8 cubic yards for the 24 x 24 ft floor at 4 in with 10% waste, $1,200 delivered at $150 a yard; the 12 x 20 ft floor is 3.5 yards and pays the $75 short-load fee, $600 in all (147 bags of 80 lb, which is why nobody uses bags). Most garage floors are poured 5 in with a thickened edge; the garage floor guide has those volumes.
What is not in these figures?: The footing (sized by the code or an engineer for a building, not by the garden-wall rule), the rebar itself, the roof, the doors and windows, lintels over the openings, anchor bolts, stucco or paint, the permit and the labor. HomeGuide's $5 to $10 per block to lay is $3,355 to $6,710 on the 24 x 24 ft garage's 671 blocks.

How many concrete blocks do I need for a wall?
8x8x16 blocks per square foot and for walls from 10x4 to 40x8 ft with 5% waste, mortar volume, and the metric 440 x 215 mm block per square metre.
How much concrete to fill cinder blocks? (per block, per 100, per wall)
Grout per 8 in block (0.22 cu ft, three blocks per 80 lb bag), per 100 blocks and for 10 to 40 ft walls with every cell filled or bars every 16 to 48 in, plus metric.
How much does a cinder block wall cost? (materials per wall and per square foot)
Blocks, mortar and grout priced for walls from 10x4 to 40x8 ft at 2026 shelf prices, materials per square foot, what grouting adds, and HomeGuide's installed range.
Building a block wall: courses, rebar, grout and mortar for a 20 ft wall
The material list for a CMU wall in order: footing, courses, half blocks, bars every 32 or 48 in, grouted cells, bond beam and mortar, with counts for 4 to 8 ft walls.

Last updated 2026-09-22. Figures are planning estimates from typical product data: check the yield, size or coverage printed on what you buy and round up.