How to Read Industrial and Automotive Bearing Codes (2026)
Standard industrial bearing codes, such as 6204 or 22210, are a combination of numbers and letters that indicate the bearing type, dimension series, bore size, and protective features. Knowing how to read bearing codes is very important for workshop technicians and purchasing departments to avoid mistakes in ordering spare parts. Buying the wrong specification wastes the budget and causes machine downtime (downtime).
This guide thoroughly explains the meaning of numbers and letters on bearings, from calculating the inner diameter to protective codes like 2RS and ZZ. Understand this system to match the exact specifications from the HI-TEC ASIA catalog which has more than 2,000 variants.
How to read standard industrial bearing codes?
Standard industrial bearing codes, such as 6204 or 22210, are a combination of numbers and letters that indicate the bearing type, dimension series, bore size, and protective features. This numbering system is read from left to right to accurately identify the physical component.
The first digit indicates the bearing type. For example, "6" represents a deep groove ball bearing, while "3" represents a tapered roller bearing. The next digits indicate the dimension series which reflects the bearing's resistance to radial and axial loads.
The last two digits are the most crucial because they indicate the bore size. Finally, the letters after the numbers are suffixes that describe extra protective features. Understanding the meaning of bearing codes helps technicians match the exact spare part specifications from the HI-TEC ASIA bearing product catalog with more than 2,000 variants. HI-TEC and HI-TEC SILVER bearings ensure machines operate quietly and reliably.
What is the size of bearing 6205 and how to calculate the bore diameter?
In the bearing code 6205, the last two digits are multiplied by five to determine the bore size, so the inner diameter is 25 millimeters[1][2]. This multiplication by five rule generally applies to bearings with the last two digits ranging from 04 and above[3].
Here are the steps to calculate the bore diameter: 1. Check the last two digits: Look at the last two numbers on your rolling bearing code. 2. Small size exceptions: If the numbers are 00, 01, 02, or 03, the size is not multiplied by five. Respectively, the sizes are 10 mm, 12 mm, 15 mm, and 17 mm[4][2][3]. 3. Multiplication by five formula: For numbers 04 and above, multiply by 5. For example, code 04 means 20 mm, and 08 means 40 mm[1][2][3].
For example, if you need a 6205 bearing, you will know that the required shaft is 25 mm. Choosing the right size prevents premature wear of your industrial machine.
What do the letter codes 2RS, ZZ, and C3 mean on bearings?
Letter codes or suffixes at the end of a bearing number, such as 2RS for rubber seals or ZZ for metal shields, indicate the type of protective closure for the component[4][5]. These suffixes greatly determine the bearing's resistance to dust and water.
| Suffix Code | Meaning and Function | Application |
|---|---|---|
| 2RS | Rubber seals on both sides of the bearing[4][6][5]. | Prevents water ingress; ideal for wet environments. |
| ZZ (or 2Z) | Metal shields on both sides[4][7][5]. | Withstands coarse dust at high rotational speeds (rpm). |
| C3 | Radial internal clearance greater than standard[4][7][5]. | High-temperature environments that cause expansion. |
The C3 code indicates internal clearance greater than standard, typically used for high-speed or high-temperature applications[4][7]. ZZ and 2RS are protective codes, while C3 is a clearance class, so they are often combined into 6205 ZZ C3[7][5]. Choosing the right seal retains the grease and prevents bearing failure.
How to manually measure a bearing if the code is erased?
Manual measurement requires three main dimensions: inner diameter (d), outer diameter (D), and width/thickness (B). If the machine bearing code is erased, you must perform physical measurement using precision tools like a vernier caliper.
Measurement criteria that must be performed: - Inner Diameter (Bore - d): Measure the hole of the inner ring where the shaft is inserted. - Outer Diameter (D): Measure the outermost side of the outer ring for bearing housing compatibility. - Width (B): Measure the distance between the front and back faces of the outer ring.
These manual measurement results are then matched with standard dimension tables to identify the exact original bearing code. For example, d = 25 mm, D = 52 mm, and B = 15 mm is the 6205 series. If you have difficulty identifying the part, contact HI-TEC ASIA customer service for guidance on selecting premium HI-TEC SILVER bearings.
Frequently Asked Questions
How to read a bearing code?
Reading a bearing code is done from left to right. The first digit indicates the bearing type, the next the dimension series, the last two digits indicate the bore size, and the letters at the end indicate the type of shield.
What do 2RS, ZZ, and C3 mean on a bearing?
The 2RS code means the bearing has rubber seals on both sides, while ZZ is protected by metal shields[4][5]. The C3 code indicates a radial internal clearance greater than standard to accommodate thermal expansion[4][7].
What is the size of bearing 6205 in mm?
The bore or inner diameter of bearing 6205 is 25 mm, obtained by multiplying the last two digits (05) by five[1][2].
How to manually measure a bearing?
Use a vernier caliper to measure the inner diameter, outer diameter, and width of the bearing. Match these three numbers with a standard dimension table to find the correct code.
References
- How to Calculate the Correct Bearing Size for Your Application. https://fytzbearing.com/how-to-calculate-the-correct-bearing-size-for-your-application/ (2024-04-01)
- Ball Bearing Measurement, Bearing Sizes & Bearing Codes | RS. https://uk.rs-online.com/web/content/discovery/ideas-and-advice/how-to-measure-a-ball-bearing (2023-10-13)
- [PDF] Roller and Ball Bearings Design Guide. https://www.nhbb.com/sites/nhbb/files/2020-05/nhbb-large-ball-and-roller-bearing-products-and-engineering-catalog-2010.pdf (2026-06-20)
- Bearing number | Basic Bearing Knowledge. https://koyo.jtekt.co.jp/en/support/bearing-knowledge/6-3000.html (2026-06-26)
- [PDF] Designations suffixes formatted. https://www.rmbearings.co.uk/pictures/pdfs/SKF%20DESIGNATIONS.pdf (2025-10-04)
- What do those codes on Bearing mean ? 6309 2Z/C3. https://onebyzeroelectronics.blogspot.com/2020/10/what-do-those-codes-on-bearing-mean.html (2020-11-01)
- How to Choose Bearing ZZ, 2RS, Open, and C3? Complete Guide to .... https://iskbearing.com/news/knowledge/bearing-zz-2rs-open-c3-selection-guide (2026-05-25)