How to Read Bearing Number : 4 Steps To Identify Correctly & Avoid Mistakes

How to read bearing number is an important skill for engineers, maintenance technicians, machine operators, and industrial buyers. A bearing number is not just a random combination of numbers and letters. It usually contains information about the bearing series, bore size, seal or shield type, internal clearance, and other design features.

For example, a bearing marked 6205-2RS-C3 can tell you several important things about the bearing before you even open its packaging. However, bearing numbering systems are not completely universal: the exact meaning of suffixes and prefixes can vary between manufacturers. Therefore, the manufacturer’s catalogue should always be used for final identification.

In this guide, we will explain bearing numbers step by step, using practical examples, bearing size data, common codes, and selection tips.

What Is a Bearing Number?

A bearing number is an identification code assigned to a rolling bearing. It helps identify the bearing’s basic design and, depending on the manufacturer, additional features such as:

• Bearing type
• Dimension series
• Bore diameter
• Seal or shield arrangement
• Internal clearance
• Retainer/cage design
• Accuracy or precision class
• Lubrication
• Special design features

A typical bearing designation may look like: 6205-2RS-C3

• The code can be divided into different sections:
• 62 | 05 | 2RS | C3
• Each section provides different information.
• Important: The interpretation of a bearing designation depends on the manufacturer. Codes such as 2RS, ZZ, C3, P6, P5, N, NR and others can have manufacturer-specific definitions.

Why Is It Important to Read Bearing Numbers?

Correctly identifying a bearing can prevent costly installation and maintenance mistakes.

If you replace a bearing with the wrong:

• Bore diameter
• Outside diameter
• Width
• Clearance
• Seal type
• Load capacity
• Speed rating

the machine may experience excessive heat, vibration, noise, premature wear, or even bearing failure.

For example : Two bearings can have the same bore diameter but completely different outside diameters and widths. They may therefore not be interchangeable.

Understanding bearing numbers helps you:

1. Identify a replacement bearing.
2. Check bearing dimensions.
3. Compare different bearing types.
4. Select the correct internal clearance.
5. Identify sealed and shielded bearings.
6. Understand bearing size codes.
7. Verify replacement parts.
8. Reduce installation errors.
9. Select bearings for specific operating conditions.
10. Compare products from different manufacturers.

Bearing Number Structure Explained

A bearing designation generally consists of: Prefix + Basic Designation + Suffix

For example: 6205-2RS-C3

Here:

• 62 = basic bearing series designation
• 05 = bore code
• 2RS = sealing designation
• C3 = internal clearance designation

However, this should be treated as a simplified interpretation rather than a universal decoding rule.

Understanding the Example: 6205-2RS-C3

Let’s break down the popular example:

1. “6” – Bearing Type / Series Family

• In many commonly used ISO-style designations for metric ball bearings, 6 identifies the family of single-row deep groove ball bearings.
• Deep groove ball bearings are widely used because they can accommodate primarily radial loads and also carry axial loads in both directions under suitable conditions.

Typical applications include:

• Electric motors
• Pumps
• Fans
• Conveyors
• Gearboxes
• Machine tools
• Industrial machinery
• Appliances
• Automotive components

2. “2” – Dimension Series

• The second digit helps identify the dimension series.
• For a 6205 bearing, the 2 belongs to the dimension series designation. Dimension series affect the relationship between bearing bore, outside diameter, and width.
• This is why a bearing’s complete designation matters.
• You should not assume that bearings with the same bore are interchangeable.
• For example, different bearing series can have the same bore but different outside diameters.

3. “05” – Bore Code

• The last two digits of many metric bearing designations indicate the bore code.
• For standard metric bearings with bore codes from 04 onward, a commonly used rule is:
• Bore diameter = bore code × 5 mm
• Therefore: 05 × 5 = 25 mm
• So a standard 6205 bearing has a nominal bore of: 25 mm

This is one of the most useful bearing-number rules.

Bearing Bore Code Chart

Here is a useful basic reference:

Bore Code	Bore Diameter
00	10 mm
01	12 mm
02	15 mm
03	17 mm
04	20 mm
05	25 mm
06	30 mm
07	35 mm
08	40 mm
09	45 mm
10	50 mm
11	55 mm
12	60 mm
13	65 mm
14	70 mm
15	75 mm
16	80 mm

For bore codes 04 and above, the common calculation is: Bore diameter = code × 5 mm

For example:

• 6208 Bore = 08 × 5 = 40 mm
• 6210 Bore = 10 × 5 = 50 mm
• 6212 Bore = 12 × 5 = 60 mm

Important exception

Codes 00, 01, 02 and 03 do not follow the ×5 rule.

They correspond to:

• 00 = 10 mm
• 01 = 12 mm
• 02 = 15 mm
• 03 = 17 mm

Always verify the manufacturer’s dimensional table before ordering.

What Does “2RS” Mean on a Bearing?

In many bearing catalogues, 2RS indicates a bearing with two rubber contact seals, one on each side.

For example: 6205-2RS

generally means:

• 6205 = basic bearing designation
• 2RS = sealed on both sides

Rubber seals help protect the bearing from contaminants and help retain lubricant.

They are particularly useful in environments where bearings may encounter:

• Dust
• Dirt
• Moisture
• Light splashing
• Industrial contaminants

However, the exact seal designation can vary by manufacturer.

What Does “ZZ” Mean?

ZZ is commonly used to indicate a bearing with metal shields on both sides.

For example: 6205-ZZ

generally indicates:

• 6205 = bearing designation
• ZZ = metal shields on both sides

A shielded bearing and a sealed bearing are not exactly the same.

2RS vs ZZ

Feature	2RS	ZZ
Protection	Rubber seals	Metal shields
Contact	Generally contacting seal	Non-contact/close metal shield arrangement
Contaminant protection	Generally better	Generally lower than a contact seal in dirty environments
Friction	Usually somewhat higher	Usually lower
Typical use	Dust/moisture environments	Cleaner, higher-speed applications

The exact performance depends on bearing design and manufacturer specifications.

What Does C3 Mean on a Bearing?

C3 means the bearing has greater-than-normal internal radial clearance. It is commonly used in applications involving higher operating temperatures, higher speeds, or thermal expansion, where standard clearance may be insufficient.

For example: 6205-2RS-C3

means the bearing has a C3 internal clearance specification in addition to its basic designation and seal arrangement.

Internal clearance is the total amount of movement possible between the bearing’s rings and rolling elements before the bearing is installed and operating.

Why is clearance important?

Because bearing operating temperature, shaft and housing fits, speed, load, and thermal expansion can affect the final operating clearance.

C3 clearance is commonly selected in applications where additional clearance is required due to operating conditions, but it should not be selected simply because “C3 is better.”

The correct clearance depends on the application.

CN vs C3 vs C4

A simplified comparison is:

Clearance	Meaning
C2	Less than normal clearance
CN / Normal	Normal clearance
C3	Greater than normal
C4	Greater than C3
C5	Greater than C4

The correct choice depends on:

• Operating temperature
• Shaft fit
• Housing fit
• Speed
• Load
• Thermal expansion
• Operating conditions

Using excessive clearance can be just as undesirable as using insufficient clearance.

What Is the Difference Between Bearing ID, OD and Width?

When reading bearing specifications, three dimensions are especially important:

ID – Inner Diameter

• The ID is the bore through the center of the bearing.
• For a 6205 bearing: ID = 25 mm

OD – Outside Diameter

• The OD is the outside diameter of the bearing.

Width

• Width is the axial thickness of the bearing.
• A commonly specified 6205 deep groove ball bearing has approximately: 25 mm ID × 52 mm OD × 15 mm width
• This is often written as: 25 × 52 × 15 mm

Always confirm dimensions against the specific manufacturer’s catalogue.

Common Bearing Size Examples

Some commonly encountered deep groove ball bearings include:

Bearing Number	Bore Code	ID (mm)	OD (mm)	Width (mm)
6000	00	10	26	8
6001	01	12	28	8
6002	02	15	32	9
6003	03	17	35	10
6004	04	20	42	12
6005	05	25	47	12
6006	06	30	55	13
6007	07	35	62	14
6008	08	40	68	15
6200	00	10	30	9
6201	01	12	32	10
6202	02	15	35	11
6203	03	17	40	12
6204	04	20	47	14
6205	05	25	52	15
6206	06	30	62	16
6207	07	35	72	17
6208	08	40	80	18
6209	09	45	85	19
6210	10	50	90	20
6211	11	55	100	21
6212	12	60	110	22
6304	04	20	52	15
6305	05	25	62	17
6306	06	30	72	19
6307	07	35	80	21
6308	08	40	90	23
6309	09	45	100	25
6310	10	50	110	27
6311	11	55	120	29
6312	12	60	130	31

These are commonly published standard dimensions, but product specifications should always be checked before purchase because designation details can differ across bearing types and manufacturers.

How to Decode Bearing Number ?

Bearing numbers contain important information about the bearing type, series, bore size, seals and internal clearance. By understanding each part of the designation, you can identify the correct bearing quickly and avoid costly selection mistakes.

Example 1: Decode 6205-2RS-C3

Let’s decode the complete example.

Step 1: Identify the basic bearing

• 6 → deep groove ball bearing family

Step 2: Identify the dimension series

• 2 → dimension series

Step 3: Calculate bore

• 05 × 5 = 25 mm
• Therefore: ID = 25 mm

Step 4: Identify sealing

• 2RS → commonly two rubber seals

Step 5: Identify clearance

C3 → greater-than-normal internal clearance. Therefore, the designation provides a useful initial description of the bearing. But for final selection, you should still verify:

• OD
• Width
• Dynamic load rating
• Static load rating
• Limiting/reference speed
• Seal specification
• Clearance specification
• Tolerance class
• Lubrication

Example 2: Decode 6208-ZZ

• Basic bearing designation : 6208
• Bore code: 08
• 08 × 5 = 40 mm
• Therefore: ID = 40 mm
• ZZ : Metal shields on both sides in many manufacturer’s designation systems.
• So the bearing is generally a shielded deep groove ball bearing with a 40 mm nominal bore.

Example 3: Decode 6306-2RS-C3

Here:

• 6 = deep groove ball bearing family
• 3 = dimension series
• 06 = 30 mm bore
• 2RS = commonly two rubber seals
• C3 = greater-than-normal internal clearance

Bore: 06 × 5 = 30 mm

Notice that changing the series from 62 to 63 can change the bearing’s outside diameter, width, load capacity and other characteristics.

Therefore: Never select a bearing based only on bore diameter.

What Are Bearing Prefixes and Suffixes?

Not every bearing designation starts directly with the basic bearing number. Manufacturers may use prefixes and suffixes to describe special features.

Prefixes

A prefix can identify:

• Special material
• Bearing design
• Component
• Manufacturing variation
• Special internal construction

Suffixes

Suffixes can identify:

• Seals
• Shields
• Clearance
• Cage
• Accuracy
• Lubrication
• Snap ring
• Special design

Common designations that buyers encounter include: 2RS, ZZ, C3, C4, P6, P5, NR, N

However, these codes are not universally identical across every brand. For example, one manufacturer’s suffix may differ from another manufacturer’s suffix.

Why Bearing Codes Can Be Confusing

One of the biggest mistakes is assuming that every manufacturer uses exactly the same designation system.

The basic designation may follow international conventions, while suffixes and special designations can be manufacturer-specific.

Therefore: Bearing number decoding should be treated as a first identification step—not a substitute for the manufacturer’s catalogue.

If you are buying a replacement bearing, verify the manufacturer’s:

• Part number
• Dimensions
• Load rating
• Clearance
• Seal/shield arrangement
• Speed rating
• Material
• Precision class

How to Read a Bearing Number Step by Step

Use this simple process whenever you find an unfamiliar bearing.

Step 1: Write Down the Complete Bearing Number

• Do not record only the first four digits.
• For example:
• 6205-2RS-C3
• The suffixes can be critical.

Step 2: Identify the Basic Bearing Type

Look at the main designation and determine whether it is:

• Deep groove ball bearing
• Angular contact ball bearing
• Self-aligning bearing
• Cylindrical roller bearing
• Tapered roller bearing
• Spherical roller bearing
• Thrust bearing

Step 3: Identify the Bore Code

• For many standard metric bearings:
• Bore = code × 5 mm
• Remember the exceptions for 00–03.

Step 4: Check the Bearing Dimensions

Step 5: Check Seals or Shields

Look for designations such as:

• 2RS
• ZZ
• Z
• Open

Verify the exact meaning with the manufacturer’s catalogue.

Step 6: Check Internal Clearance

Look for:

• C2
• CN
• C3
• C4
• C5

Choose based on operating conditions rather than automatically selecting C3.

Step 7: Check Load Ratings

Look for:

• C = dynamic load rating
• C₀ = static load rating

These values are important for bearing selection and life calculations.

Step 8: Check Speed

• If the machine operates at high RPM, check the manufacturer’s speed ratings.
• Do not assume that every bearing with the same dimensions has the same allowable speed.

Step 9: Check Operating Environment

Consider:

• Dust
• Water
• Temperature
• Vibration
• Chemicals
• Shock loads
• Lubrication

These factors influence the appropriate bearing design.

Step 10: Verify the Manufacturer’s Catalogue

• This is the final and most important step.
• Compare the complete bearing number with the manufacturer’s official specification.

Bearing Number vs Bearing Size: Are They the Same?

No. A bearing number identifies a particular bearing design and configuration, while bearing size refers to its physical dimensions.

For example: 6205

• identifies a particular bearing designation.
• Its commonly specified dimensions are:
• 25 × 52 × 15 mm

Therefore:

• Bearing number = identification
• ID = inner diameter
• OD = outside diameter
• Width = bearing width

You need both identification and dimensions when selecting a replacement.

Can You Identify a Bearing Without Its Number?

Sometimes, yes. If the bearing number is unreadable, you can measure:

1. Inner diameter
2. Outside diameter
3. Width

Then compare these measurements against a bearing catalogue.

For example : suppose you measure approximately:

25 mm ID × 52 mm OD × 15 mm width

A common matching bearing designation is: 6205

But dimensions alone may not identify:

• Seal type
• Clearance
• Precision
• Internal design
• Material
• Cage design

Therefore, physical measurements are useful for narrowing down the bearing, but the complete specification should still be verified.

Common Mistakes When Reading Bearing Numbers

Mistake 1: Assuming the last two digits always mean the same thing

• The bore-code rule is useful for many standard metric bearings, but not every bearing designation follows the same simple pattern.

Mistake 2: Ignoring suffixes

• A 6205, 6205-2RS, and 6205-ZZ-C3 may have different features.

Mistake 3: Assuming C3 is always better

• C3 is not automatically better than normal clearance.

Mistake 4: Choosing only by ID

• The OD and width must also fit the shaft and housing arrangement.

Mistake 5: Ignoring operating conditions

• Temperature, speed, types of load, contamination, and lubrication can significantly affect bearing performance.

Mistake 6: Assuming all brands use identical codes

• Always check the manufacturer’s catalogue.

Conclusion

Learning how to read bearing numbers makes bearing identification, replacement and selection much easier. Learning how to read bearing numbers makes identification and replacement much easier.

A designation like 6205-2RS-C3 can indicate the bearing series, bore size, seals and internal clearance. For example, 05 usually represents a 25 mm bore in standard metric bearings, while 2RS indicates rubber seals and C3 indicates greater-than-normal internal clearance. However, always verify ID, OD, width, load ratings, speed and suffixes with the manufacturer’s catalogue before selecting a replacement.

The safest approach is simple:

Read the complete bearing number → decode the basic designation → check ID/OD/width → verify suffixes → check load and speed → confirm the manufacturer’s catalogue.

Once you understand this process, identifying common bearings becomes significantly easier and you can make more confident bearing selection decisions for industrial machinery, motors, pumps, conveyors and other rotating equipment.

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