Reference

Concrete block sizes and weights

A block is sold under a name it does not measure. An 8×8×16 is 7⁵⁄₈ inches every way it is named for, and the missing three eighths is the mortar joint that makes the module work. Cinder block, cement block, CMU and concrete masonry unit all name the same product. Here is every size a yard stocks, what each one weighs, and where the two numbers matter.

CMU and cinder block dimensions: nominal and actual

Nominal size is the module — the size the block occupies once it is laid, joint included. Actual size is what you measure with a tape. Every standard unit is 3⁄8 in under its nominal size in each direction that carries a joint.

Nominal	Actual (in)	Actual (mm)	Face area	Per 100 sq ft
4 × 8 × 16 in	3⅝ × 7⅝ × 15⅝	92 × 194 × 397	0.889 sq ft	112.5 blocks
6 × 8 × 16 in	5⅝ × 7⅝ × 15⅝	143 × 194 × 397	0.889 sq ft	112.5 blocks
8 × 8 × 16 in	7⅝ × 7⅝ × 15⅝	194 × 194 × 397	0.889 sq ft	112.5 blocks
10 × 8 × 16 in	9⅝ × 7⅝ × 15⅝	244 × 194 × 397	0.889 sq ft	112.5 blocks
12 × 8 × 16 in	11⅝ × 7⅝ × 15⅝	295 × 194 × 397	0.889 sq ft	112.5 blocks

Only the width changes across the range. Every standard unit presents the same 8 × 16 in face, so the block count for a wall is identical whether it is 4 inch or 12 inch — 1.125 blocks per square foot, 112.5 per hundred. What changes with width is the weight, the grout volume and what the wall can carry.

4 inch CMU dimensions

3⅝ × 7⅝ × 15⅝ in

Veneer backing, partition walls and infill that carries no load. Often solid rather than hollow.

6 inch CMU dimensions

5⅝ × 7⅝ × 15⅝ in

Interior partitions and garden walls a few courses high.

8 inch CMU dimensions

7⅝ × 7⅝ × 15⅝ in

The standard block: foundations, garage walls and most load-bearing work.

10 inch CMU dimensions

9⅝ × 7⅝ × 15⅝ in

Taller foundation walls and walls that need more room for grout and steel.

12 inch CMU dimensions

11⅝ × 7⅝ × 15⅝ in

Basement and retaining walls holding back soil, and tall shop walls.

Cinder block dimensions are the same numbers: a standard cinder block measures 7⅝ × 7⅝ × 15⅝ in, sold as 8 × 8 × 16. When a plan or a size chart says "8 inch block" it means the nominal width, and the tape will read 7⅝.

Choosing between the widths is mostly a question of what the wall does. A freestanding garden wall or a partition can be 6 inch; anything carrying a floor or a roof starts at 8; and a wall holding back soil goes to 10 or 12 because it needs the thickness to resist the push and the cell space for grout and vertical steel. For a wall that retains more than a few courses of earth, segmental units are often the easier build — the retaining wall calculator covers those, and the concrete block calculator counts CMU, mortar and core fill for a standard wall of any width.

Half blocks, corners and bond beams

The stretcher above is most of any wall, but not all of it. A block yard stocks the same widths in a handful of shapes, and the take-off should count them separately because they are priced separately.

Unit	Nominal size	Where it goes
Stretcher	8 × 8 × 16 in	The field of the wall
Corner	8 × 8 × 16, one flat end in	Outside corners and exposed wall ends
Half block	8 × 8 × 8 in	Finishing alternate courses at ends and openings
Bond beam	8 × 8 × 16, U-shaped in	Courses that take horizontal rebar and grout
Lintel	8 × 8 × 16, U-shaped in	Spanning door and window openings, grouted with steel
Solid or cap	4 × 8 × 16 in	Topping a wall, or where a hollow face is not wanted

Running bond puts a half block at every other course at each free end, so a straight wall with two exposed ends needs roughly one half block per end per two courses. How many bond beam courses a wall needs, and where, comes from the drawings or the local code — nearly always one at the top; the steel in them is sized in rebar sizes and weights.

Concrete and cinder block weight by size

Weight depends on the aggregate, not the shape. Normal-weight units use sand and gravel at roughly 125 lb per cubic foot; lightweight units use expanded shale or slag and come out about 25 to 30 percent lighter for the same size. Both are sold as the same nominal block.

Nominal size	Normal weight	Lightweight	Per pallet
4 × 8 × 16 in	26–28 lb	18–20 lb	120
6 × 8 × 16 in	30–32 lb	22–24 lb	108
8 × 8 × 16 in	36–38 lb	26–28 lb	90
10 × 8 × 16 in	44–46 lb	32–34 lb	72
12 × 8 × 16 in	50–55 lb	36–40 lb	60

Lightweight units are the same wall for a quarter less lifting, which over a thousand-block job is the difference between two days and three. They cost more per block and lay identically.

How many concrete blocks on a pallet

Counts fall as the block gets wider, and the reason is not the size — it is the weight. Yards build a pallet to what a forklift and a boom truck can handle safely, so every pallet in the table below lands within about two hundred pounds of the others regardless of what is stacked on it.

Nominal size	Blocks per pallet	Pallet weight	Wall it builds
4 × 8 × 16 in	120	~3 240 lb	107 sq ft
6 × 8 × 16 in	108	~3 350 lb	96 sq ft
8 × 8 × 16 in	90	~3 330 lb	80 sq ft
10 × 8 × 16 in	72	~3 240 lb	64 sq ft
12 × 8 × 16 in	60	~3 150 lb	53 sq ft

Two things follow from that column of weights. A full pallet is roughly a ton and a half, which is more than a half-ton pickup has any business carrying, so block arrives on a boom truck and gets set where it will be laid — moving it twice by hand is a day nobody planned for. And because the wall area per pallet is fixed, a pallet is a usable ordering unit in its own right: a 40 ft run of 8 inch block at 4 ft high is 160 sq ft of face, which is two pallets and a few blocks over.

Counts do vary by yard — some stack 8 inch units 96 to a pallet, some 88 — so confirm the figure before ordering by the pallet rather than by the block. The weight is the more reliable number, because it is what the handling equipment is rated for.

Course heights and coursing

Every course adds exactly 8 inches — the block plus its bed joint. That makes coursing easy to plan and easy to get wrong: a wall height that is not a multiple of 8 inches ends in a cut course, and cutting block is slow.

Courses	Height	Common use
3	2 ft 0 in	Garden wall, planter
6	4 ft 0 in	Low retaining, crawl space
9	6 ft 0 in	Privacy wall
12	8 ft 0 in	Full storey, garage wall
16	10 ft 8 in	Tall shop or basement wall

Why cinder block and concrete block are the same thing

A true cinder block used coal cinders as its aggregate, and coal ash stopped being a by-product worth collecting decades ago. What a store sells today as cinder block, cement block, CMU or concrete masonry unit is one product: a hollow concrete unit with two cells. The names survive regionally, and a supplier will know what you mean whichever one you use.

The distinction that does still matter is normal weight against lightweight, because that is a 10 lb difference on every unit you lift. On a 200 block wall it is a ton of difference over the day.

Count the blocks for your wall →

Building in brick instead? Brick dimensions and course heights covers the same ground for every named brick format. For the steel that runs through grouted cells, see rebar sizes and weights.

Put these figures to work

These are the dimensions every masonry calculator on the site runs on. Each tool applies them to one kind of wall.

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