How to Read Bearing Numbers?
Newcomers to bearings often find themselves confused by a string of numbers and letters. Actually, bearing numbers aren't random; they're a set of structured "identification codes." Once you grasp the basic rules, you can quickly determine the type, size, and structural characteristics of any bearing model.
The code consists of three parts, each containing specific information.
A complete bearing code typically consists of three parts: a prefix, a base code, and a suffix.
The prefix generally indicates the bearing's precision grade or clearance, etc.; the base code is the core part, containing the bearing's type, size series, and inner diameter information; the suffix provides further details about the internal structure, sealing method, cage material, etc.
The most common bearing models often omit the prefix, focusing primarily on the base and suffix codes.
The base code is the core:
The base code typically consists of three parts: type code, size series code, and inner diameter code.
Taking the most common 6204 as an example:
The first digit "6" represents the type, indicating a deep groove ball bearing;
The second digit "2" belongs to the size series, reflecting the bearing's width and outer diameter;
The last two digits "04" represent the inner diameter.
Let's look at other common type codes:
Starting with 3: Tapered roller bearings, such as 30208;
Starting with N: Cylindrical roller bearings, such as N2210.
Remembering the type code allows you to quickly determine which category the bearing belongs to.
Inner diameter codes follow a pattern; remembering the mnemonic makes it easier.
Inner diameter codes are often confusing, but there's a fixed calculation method.
For inner diameters between 10 and 17 mm, the corresponding relationships are as follows:
00 = 10 mm
01 = 12 mm
02 = 15 mm
03 = 17 mm
For inner diameters between 20 and 480 mm, simply multiply the last two digits by 5. For example, 04 represents 20mm, 08 represents 40mm, and 10 represents 50mm.
Following this rule, the inner diameter of 6204 is 4×5=20mm, and the inner diameter of 30208 is 8×5=40mm, which is self-explanatory.
Understand the details in the suffix designation; recognize common symbols.
Suffix designations supplement the structural and performance details of the bearing. Common symbols include:
Z, RZ, RS: Indicate the type of seal or dust cover;
C1~C5: Indicate the clearance size; the larger the number, the larger the clearance;
P0~P6: Indicate the precision class; the higher the class, the higher the precision;
Q, M, L, N: Usually related to the cage material or structure.
These suffixes, though short, directly affect the bearing's applicable scenarios and cannot be ignored during procurement and replacement.
Quickly determine the bearing type with the model number.
Understanding bearing designations essentially involves three steps: first, look at the type; second, look at the dimensions and inner diameter; and finally, look at the details in the suffix.
For example, seeing 6204 tells you it's a deep groove ball bearing with an inner diameter of 20mm; seeing 30208 tells you it's a tapered roller bearing with an inner diameter of 40mm. Once you master this set of rules, you can quickly identify various models and no longer be stumped by a string of numbers.
Post time: Sep-21-2026
