Concrete (Cinder) Block Sizes, Dimensions and Weights
A conventional concrete block has a nominal face 8 in[1] high by 16 in[1] long, and its actual size is typically 0.375 in[1] less in each dimension, so an 8x8x16 block measures about 7 5/8 in by 7 5/8 in by 1 ft 3 5/8 in.
Estimates for planning, not professional advice. Read the full notice.
Work it out for your own sizes
Count blocks for a wall of 8x8x16Example to try: Wall length 20 ft, Wall height 4 ft, Block 8 in
Block sizes by width: nominal, actual, face and weight
Nominal and actual width, height and length, nominal face area, and approximate weight at three concrete densities, for five block widths
| Nominal width | Actual width | Actual height | Actual length | Nominal face area | Weight at 85 lb/ft³ | Weight at 115 lb/ft³ | Weight at 135 lb/ft³ |
|---|---|---|---|---|---|---|---|
| 4 in | 3 5/8 in | 7 5/8 in | 1 ft 3 5/8 in | 0.89 ft² | 16 lb | 21 lb | 25 lb |
| 6 in | 5 5/8 in | 7 5/8 in | 1 ft 3 5/8 in | 0.89 ft² | 20 lb | 27 lb | 32 lb |
| 8 in | 7 5/8 in | 7 5/8 in | 1 ft 3 5/8 in | 0.89 ft² | 22 lb | 30 lb | 36 lb |
| 10 in | 9 5/8 in | 7 5/8 in | 1 ft 3 5/8 in | 0.89 ft² | 28 lb | 38 lb | 48 lb |
| 1 ft | 11 5/8 in | 7 5/8 in | 1 ft 3 5/8 in | 0.89 ft² | 33 lb | 44 lb | 52 lb |
Source: [2]
Actual sizes are the nominal size less the amount CMHA gives. Weights are MAC's approximate oven-dry weights for a hollow block; blocks as delivered weigh more.
Nominal and actual size
People also call concrete blocks cinder blocks; the sizes here are for concrete masonry units. Nominal widths run from 4 in[1] to 16 in[1] in steps of 2 in[1]. The block calculator counts a wall on the nominal face, because the joint is inside the nominal size, and lists the weights above for the width you pick.
Actual dimensions of concrete masonry units are typically 3/8 in. (9.5 mm) less than nominal dimensions, so that the 4 or 8-in. (102 or 203 mm) module is maintained with 3/8 in. (9.5 mm) mortar joints.
For the bags of mortar a wall takes, see the mortar calculator, and for brick, the brick sizes page.
Questions
What is the actual size of an 8x8x16 block?
About three eighths of an inch less than nominal in each dimension, as CMHA says, so the face is a little smaller than eight by sixteen. The table lists the actual sizes for each width.
How much does a cinder block weigh?
It depends on the width and on the density of the concrete. The table gives MAC's approximate oven-dry weights at three densities, and delivered blocks weigh more.
What are cinder block dimensions?
Concrete masonry units are named by nominal width, height and length, such as eight by eight by sixteen. The table gives the nominal width with the actual sizes beside it.
Are half blocks and corner blocks counted?
No. The block calculator counts blocks on the nominal face of the wall; half blocks, corner units and lintels are not counted separately.
Calculate it for your project
Enter your own sizes to get the amount to buy or the layout figures, with the working shown and a page to print.
Try your own wall in the block calculatorSources (2)
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TEK 05-12, Modular Layout of Concrete Masonry (opens in new tab), Concrete Masonry & Hardscapes Association (formerly NCMA), TEK 05-12 (web edition).
Standards or industry body.
“Typically, concrete masonry units have nominal face dimensions of (height by length) 8 by 16 in.”
“Actual dimensions of concrete masonry units are typically 3/8 in. (9.5 mm) less than nominal dimensions, so that the 4 or 8-in. (102 or 203 mm) module is maintained with 3/8 in. (9.5 mm) mortar joints.”
“… are available in nominal widths ranging from 4 in. to 16 in. … in 2-in. … increments.”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 1) -
Density-Related Properties of Concrete Masonry (Viewpoint) (opens in new tab), Masonry Advisory Council, Undated PDF; cites ASTM C90-06b and a 2007 MAC cost guide.
Standards or industry body.
“Table 1 - Approximate weight (lbs) of oven dry concrete masonry units as a function of concrete density 85 95 105 115 125 135 4 3.63 74 .250 .185 16 18 19 21 23 25 6 6.63 61 .388 .237 20 23 25 27 30 32”
“Table 1 - Approximate weight (lbs) of oven dry concrete masonry units as a function of concrete density 85 95 105 115 125 135 ... 8 7.63 52 .526 .273 22 25 28 30 33 36 10 9.63 50 .664 .332 28 32 36 38 42 48”
“Table 1 - Approximate weight (lbs) of oven dry concrete masonry units as a function of concrete density 85 95 105 115 125 135 ... 12 11.63 48 .802 .385 33 37 40 44 48 52”
Checked November 12, 2026. Figures and codes change; verify with the source. Back to where this is used (Source 2)
These are summaries of what the sources say, not professional advice. Codes and product data change. Check with your building department and the product label about your own project.