This CMU block sizes chart compares common U.S. nominal sizes with typical specified dimensions. Standard modular units are often listed as 4, 6, 8, 10, or 12 inches wide by 8 inches high and 16 inches long. In a common size such as 8 × 8 × 16 inches, the physical unit is typically 7 5/8 × 7 5/8 × 15 5/8 inches. The nominal size is used for planning; confirm the manufacturer’s exact dimensions for a purchase or tight fit.
Standard CMU Block Sizes Chart
Sizes below are written width × height × length. The metric figures are rounded conversions of the typical specified dimensions.
| Nominal size (W × H × L) | Typical specified dimensions (W × H × L) | Approx. specified dimensions (mm) |
|---|---|---|
| 4 × 8 × 16 in. | 3 5/8 × 7 5/8 × 15 5/8 in. | 92 × 194 × 397 mm |
| 6 × 8 × 16 in. | 5 5/8 × 7 5/8 × 15 5/8 in. | 143 × 194 × 397 mm |
| 8 × 8 × 16 in. | 7 5/8 × 7 5/8 × 15 5/8 in. | 194 × 194 × 397 mm |
| 10 × 8 × 16 in. | 9 5/8 × 7 5/8 × 15 5/8 in. | 244 × 194 × 397 mm |
| 12 × 8 × 16 in. | 11 5/8 × 7 5/8 × 15 5/8 in. | 295 × 194 × 397 mm |
Nominal widths of 4, 6, 8, 10, and 12 inches are common. Some producers also offer 14- and 16-inch specialty widths, nonstandard heights or lengths, and units shaped for particular wall details. Availability depends on the region and producer.
How to Read a CMU Size
A size written as 8 × 8 × 16 inches usually means 8 inches thick (wall width), 8 inches high, and 16 inches long. The first number is the wall thickness for a single wythe. The other two numbers describe the unit face and course layout. Manufacturers may present the order differently, so check the W × H × L labels on a product sheet.
The 8 × 8 × 16 nominal unit is a common standard size. Its typical specified dimensions are 7 5/8 inches wide, 7 5/8 inches high, and 15 5/8 inches long. For its measurements and related details, see our 8×8×16 CMU dimensions guide.
Nominal vs. Specified CMU Dimensions
Nominal dimensions are the module used to lay out masonry. For typical modular CMU, the specified unit is about 3/8 inch smaller in each dimension so a standard mortar joint can bring the installed module close to the nominal increment. For example, a 15 5/8-inch unit plus a typical 3/8-inch joint fits a 16-inch course module.
“Actual” is often used informally for a measured unit, while product sheets list its specified dimensions. For standard precision CMUs specified to ASTM C90, no overall width, height, or length may differ from the specified dimension by more than ±1/8 inch (3.2 mm). Specialty products or finishes may have different dimensional rules. This tolerance applies to the manufactured unit, not the mortar joint. Treat the chart as typical and check the chosen product data for openings and clearances. Read more in our CMU nominal vs. actual dimensions guide.
Common CMU Variations
A full-size stretcher is only one unit in a CMU system. Half-high and half-length units can finish a course or fit a planned module without field-cutting a full block. These examples are common nominal sizes; specified dimensions and availability depend on the manufacturer.
| Common unit (nominal W × H × L) | Typical specified dimensions | Typical use |
|---|---|---|
| Half-high: 8 × 4 × 16 in. | 7 5/8 × 3 5/8 × 15 5/8 in. | Build a shorter course on a 4-inch vertical module |
| Half-length: 8 × 8 × 8 in. | 7 5/8 × 7 5/8 × 7 5/8 in. | Finish a course or wall end without cutting a full-length unit |
Concrete block weight also changes with aggregate, density, cores, and whether a unit is solid or hollow. The sizes chart is not a reliable weight chart. Use the supplier’s specifications or our CMU block weight guide for weight estimates. Pallet counts likewise vary by producer; see how many CMU blocks are on a pallet.
How Many CMU Blocks Cover One Square Foot?
A nominal 8 × 16-inch face module covers 128 square inches. Dividing 144 square inches in one square foot by 128 gives about 1.125 standard face modules per square foot, before subtracting openings or adding a waste allowance. Treat this as a rough quantity estimate only; bond pattern, corners, cuts, openings, and unit size change the takeoff. Use our CMU block calculator for a wall-specific estimate.
How to Choose a CMU Size
Use the size shown in the wall schedule or project drawings. If you are comparing products, check the nominal size, specified dimensions, unit weight, core layout, finish, and local availability. Wall thickness alone does not determine a wall’s strength or whether a unit is appropriate for a structural use; that depends on the complete wall design, loads, reinforcement, grout, supports, and applicable code. See the CMU wall thickness chart for unit width versus finished wall depth.
Frequently Asked Questions
What is the most common CMU block size?
The 8 × 8 × 16-inch nominal CMU is a common standard unit. Its typical specified dimensions are 7 5/8 × 7 5/8 × 15 5/8 inches. Confirm the exact size and availability with the local manufacturer.
Why are CMU blocks smaller than their nominal size?
The nominal dimension is the modular planning size. A typical 3/8-inch allowance for a mortar joint makes the smaller specified unit fit that module.
Are all concrete blocks 8 × 8 × 16 inches?
No. Common widths include 4, 6, 8, 10, and 12 inches, and producers may stock other heights, lengths, or specialty shapes. The chart above shows common full-size modular units.
What is the actual size of a 4-inch CMU?
A common 4 × 8 × 16-inch nominal CMU is typically 3 5/8 × 7 5/8 × 15 5/8 inches as a unit. Check the specific product sheet for tolerances.
Does block size tell me its weight or strength?
No. Size alone does not establish weight or wall strength. Unit density, aggregate, core design, compressive properties, mortar, reinforcement, grout, and the wall design all matter. Use the manufacturer’s data and project specifications.
Related CMU Guides
- Standard Cinder Block Sizes
- CMU Wall Thickness Chart
- 8×8×16 CMU Block Dimensions
- CMU Block Weight Guide
Use nominal dimensions for preliminary layout, then verify the specified unit and wall assembly before ordering or setting clearances.