Brick and Block: Sizes, and Why One Tolerance Figure Cannot Exist

Every specified dimension and how it courses out, the nominal-equals-specified-plus-joint rule, and the reason nobody can honestly quote you a single tolerance number for brick.

Brick: specified size, and how it courses

Modular	3-5/8 x 2-1/4 x 7-5/8 in. 3 courses to 8 in
Engineer modular	3-5/8 x 2-13/16 x 7-5/8 in. 5 courses to 16 in
Utility	3-5/8 x 3-5/8 x 11-5/8 in. 1 course to 4 in
Why the course figure matters more	The unit size is chosen so a whole number of courses lands on a whole number of inches with a standard joint. Change the joint and the coursing stops working, which is what you notice on site, not the unit dimension.

Nominal, specified, actual

Nominal	The specified size PLUS the joint. A number for setting out, not a number you can measure on a pallet.
Specified	What the unit is made to. This is the figure in the table above.
Concrete block	Actual is nominal minus 3/8 in, every direction. A nominal 8 x 8 x 16 block is 7-5/8 x 7-5/8 x 15-5/8.
The 3/8 in is not slop	It is the joint. The block and the joint together make the nominal figure, which is why block layouts work in whole 8-inch modules.

Why there is no single tolerance for brick, and this is the point of the card

"Brick" is not one specification. The IRC names ASTM C62 (building brick), C216 (facing brick) and C652 (hollow brick) as three separate standards, alongside C34, C56, C126, C212, C1088 and C1405, all at R606.2.2. They do not share one tolerance.
C216 alone splits into appearance types, FBX, FBS and FBA, and those types carry DIFFERENT dimensional tolerances. The permitted variation also changes with the size of the dimension being measured, so it is a table, not a number.
So a single figure like "plus or minus 1/8 in on length" cannot be right for brick generally. Printed on a card it tells some readers their delivery is out of spec when it is in, and others the reverse.
The answer to "is this delivery in spec?" starts with the TYPE DESIGNATION on your submittal or order, not with the pallet. If nobody specified a type, nobody has specified a tolerance either, and that is worth raising before the load arrives rather than after.
Anyone who quotes you one tolerance number for brick has flattened three standards and several types into one figure.

The chain: what actually binds you

What binds you	The building code your jurisdiction adopted.
What the code does	It names the ASTM specification each unit must conform to. IRC R606.2.1 for concrete masonry units: ASTM C55, C73, C90, C744 or C1634. IRC R606.2.2 for clay or shale units: the list above.
What the ASTM does	Sets the material, grade, appearance type and the tolerance table. It is behind a paywall.
Mortar, where the free route exists	IRC R606.2.8 lets you comply by the PROPORTION specification in the code's own table, or by the property specification of ASTM C270. The proportion route is printed in the code. You do not have to buy C270 to specify mortar.
Practical effect	You almost never need to own the ASTM. You need to know which one your code names, and to make the supplier state on paper which standard and type he is shipping.

If you trained in the UK, compare like for like

UK actual brick	215 x 102.5 x 65 mm. What you can measure.
UK co-ordinating	225 x 112.5 x 75 mm. The brick plus a 10 mm joint.
The mistake	The 225 figure is the one usually quoted, and it is the CO-ORDINATING size. Set it against a US specified size and you are comparing a brick-with-its-joint against a brick.
Compare these instead	UK co-ordinating against US nominal. UK actual against US specified.
The real difference	A UK brick is taller and shorter than a US modular. Coursing, bond and cut sizes all change with it, so a UK setting-out rule of thumb does not survive the crossing.

The ASTM tolerance tables are deliberately not reproduced here: they are paywalled, we have not read them, and a single figure would be wrong for most readers. Section numbers are from the 2021 IRC as published for an adopting state, and the IRC is a model code, so what binds you is the edition your state or county adopted and any local amendment to it. Structural masonry design, veneer anchorage, lintels, reinforcement and cold-weather working are all governed by provisions not pulled here. Confirm your adopted edition with your building department.

Sources: iccsafe.org · astm.org

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