• Published 13 Oct 2023
    • Last Modified 12 Feb 2024
  • 14 min

A Complete Guide To Ball Bearing Measurement, Bearing Sizes And Bearing Codes

Measuring a Ball Bearing using a caliper

Ball bearings are essential components in many mechanical systems, including vehicles, industrial machinery, and household appliances. They help reduce friction and allow for smooth movement between two surfaces. Selecting the correct ball bearing is vital for various reasons, as it directly affects the performance, efficiency, safety, and potential downtime of a wide range of machines and equipment. To ensure proper functioning, it is important to know the type and size of a ball bearing.

This guide aims to assist, you the customer in measuring ball bearings accurately to make sure you select the correct bearing for your specific application. Proper measurement is crucial in identifying the appropriate ball bearing size and type, as well as interpreting bearing codes to make an informed choice. Let’s go through the step-by-step process of measuring a ball bearing and understanding bearing codes.

Identify The Type Of Ball Bearing

Before measuring, it’s important to identify the type of ball bearing you have. There are several common types, such as deep groove ball bearings, angular contact ball bearings, and thrust ball bearings to mention a few. Each type has its own unique design, and it is essential to recognize the correct type you have for accurate measurements. For more information on the different types of ball bearings available please see our Ball Bearings Guide

How To Measure A Ball Bearing

Ball bearings usually have their identification code stamped or lasered on the outside diameter of the bearing itself, using this is the best way to ensure you select the right bearing.

However, this code can become illegible or possibly worn away over time. So, it is important to measure a ball bearing correctly.

The size of a ball bearing can be determined by measuring its outer diameter (OD), bore size (ID), and width. These measurements are usually expressed in millimetres (mm). Using a calliper or a micrometer, you can accurately measure these dimensions.

Tools you’ll need to measure a ball bearing

  1. Calliper or Micrometer (digital or manual)
  2. Notepad and pen for recording data
  3. Flat and clean surface for measurement

Step 1: Prepare Your Equipment

Zero or calibrate your digital calliper or micrometer according to the manufactures instructions.

Step 2: Measure The Bore Size - Inner Diameter (ID)

Place the ball bearing on a flat and clean surface. Take the caliper or micrometer and gently insert its jaws or anvils into the bore of the bearing. Ensure that the measuring tool is at a right angle to the bore. Once positioned correctly, read, and record the measurement displayed on the caliper or micrometer. This value represents the bore size or the Inner Diameter (ID) of the bearing.

Step 3: Measure The Outer Diameter (OD)

Next, measure the outer diameter of the ball bearing. Position the measuring tool on the flat surface and place the outer edges of the caliper or micrometer jaws or anvils against the opposite sides of the bearings outer surface. Ensure the tool is at a right angle to the bearing. Read and record the measurement displayed on the caliper or micrometer. This value represents the outer diameter of the bearing.

Step 4: Measure The Width (thickness)

For ball bearings with a cylindrical shape, measure the width or thickness of the bearing. Place the bearing on a flat clean surface and align the jaws or anvils of the measuring tool against opposite sides of the bearing. Read and record the measurement displayed on the caliper or micrometer. This value represents the width of the bearing.

Bearing Codes

So, what does the code on your bearing actually signify? Let’s dig a little deeper and explain in a bit more detail.

Typically bearing codes are comprised of a ‘basic number’ and depending on the bearing they can have supplementary codes at the beginning or the end of the basic number. These are the prefix and suffix codes.

The basic number will give you general information about the bearing such as the type, series number and bore size.

We will use a popular bearing (S) (6001) (2RS) as our example

bearing code image reference

Start by breaking down the code on your bearing into 3 parts

  1. S (prefix)
  2. 6001 (basic number)
  3. 2RS (suffix)

Prefix

Bearings very rarely have a prefix code. However, you may come across one that does. The prefix is used to highlight the parts used by the manufacturer in the design of the bearing. In our example where we have a Prefix of (S) it tells us that the bearing was made using stainless steel. Below are a couple of common examples

Prefix
Meaning
WStainless Steel (SKF)
SStainless Steel (FAG)

Basic Number First Digit

The first digit of the basic number tells you about the type of bearing you have. In our example, it’s (6) So this tells us it’s a Single row deep groove ball bearing.

Bearing Type Code
Bearing Name
1Self-aligning Ball Bearing
2Spherical Roller Bearing
3Double Row Angular Contact Ball Bearing
4Double Row Ball Bearing
5Thrust Ball Bearing
6Single Row Deep Groove Ball Bearing
7Single Row Angular Contact Bearing
8Felt Seal Bearing
NCylindrical Roller Bearing
NNDouble Row Roller Bearing
NANeedle Roller Bearing
BKNeedle Roller Bearing with closed end (drawn cup)
HKNeedle Roller Bearing with open ends (drawn cup)
CCARB Toroidal Roller Bearings
QJFour-point Contact Ball Bearing

Basic Number Second Digit

The second digit of the basic number tells us what series the bearing is from and is used to signify how tough the bearing is. In our example, it’s (0) Which tells us its extra light toughness.

Series Code
Series Code Meaning
0Extra Light
1Extra Light Thrust
2Light
3Medium
4Heavy
8Extra Thin Section
9Very Thin Section

Basic Number Third And Fourth Digit

The third and fourth digits tell you the bore size or (ID) of the bearing you have. In our example, it’s (0) which tells us the bearing has a 12 mm bore size.

Important Note that from 20mm and above you would need to times (x) the last 2 digits by 5 to ascertain the bore size for nearly all types of bearing.

Third and Fourth Digit
Bore Size (mm)
0010
0112
0215
0317
From hereafter (x5)
0420
0525
And so on………

Suffix

Suffixes indicate bearings with additional special characteristics or designs. They are typically used to provide information about how the bearing is sealed. In our example, it’s (2RS) which tells us our bearing is sealed on both sides.

Suffix
What do they mean?
ZOne side of the bearing is shielded
ZZBoth sides of the bearing is shielded
RSOne side of the bearing is sealed
2RS or DDUBoth sides of the bearing is sealed
C3Larger clearance
KTaper bore
NRSnap ring groove
M or MBMachined brass cage

Clearance Codes

In some cases, your bearing may have an additional suffix such as C3. This can be found on the outside diameter of the bearing except in the case of CN. This refers to the bearings clearance code. See the table below for examples.

clearance Image
Suffix
Clearance
C1Less than C2
C2Less than normal
CNNormal
C3Greater than normal
C4Greater than C3
C5Greater than C4

It is important to note that different manufacturers can have their own specific Prefix and Suffix codes. Our tables give you some examples of the most common codes. If in doubt please check with the manufacturer of your bearing for exact information.

Ball Bearings Size Chart

So now you have a better understanding of how to measure a ball bearing and how to interpret a bearing code, why not check out our great range of high-quality bearings from industry-leading brands such as SKF, NSK, FAG, INA and of course our own brand RS PRO.

We have created a list of the most popular sizes to make it quicker and easier for you to identify and purchase the exact ball bearing for your application. Simply click on your size and view our current selection.

Single Row Deep Groove Ball Bearing Measurements

Size
Inner Dimension (mm)
Outer Dimension (mm)
Width (mm)
6044124Shop All 604 Bearings
6066176Shop All 606 Bearings
6077196Shop All 607 Bearings
6088227Shop All 608 Bearings
6099247Shop All 609 Bearings
6233104Shop All 623 Bearings
6244135Shop All 624 Bearings
6255165Shop All 625 Bearings
6266196Shop All 626 Bearings
6277227Shop All 627 Bearings
6288165Shop All 628 Bearings
6299268Shop All 629 Bearings
6866135Shop All 686 Bearings
600010268Shop All 6000 Bearings
600112288Shop All 6001 Bearings
600215329Shop All 6002 Bearings
6003173510Shop All 6003 Bearings
6004204212Shop All 6004 Bearings
6005254712Shop All 6005 Bearings
6006305513Shop All 6006 Bearings
6007356214Shop All 6007 Bearings
6008406815Shop All 6008 Bearings
6009457516Shop All 6009 Bearings
6010508016Shop All 6010 Bearings
6011559018Shop All 6011 Bearings
6012609518Shop All 6012 Bearings
60136510018Shop All 6013 Bearings
60147011020Shop All 6014 Bearings
60157511520Shop All 6015 Bearings
60168012522Shop All 6016 Bearings
60178513022Shop All 6017 Bearings
60189014024Shop All 6018 Bearings
602010015016Shop All 6020 Bearings
620010309Shop All 6200 Bearings
6201123210Shop All 6201 Bearings
6202153511Shop All 6202 Bearings
6203174012Shop All 6203 Bearings
6204204714Shop All 6204 Bearings
6205475215Shop All 6205 Bearings
6206306216Shop All 6206 Bearings
6207357217Shop All 6207 Bearings
6208408018Shop All 6208 Bearings
6209458519Shop All 6209 Bearings
6210509020Shop All 6210 Bearings
62115510021Shop All 6211 Bearings
62126011022Shop All 6212 Bearings
62136512023Shop All 6213 Bearings
62147012524Shop All 6214 Bearings
62157513025Shop All 6215 Bearings
62168014026Shop All 6216 Bearings
62178515028Shop All 6217 Bearings
62189016030Shop All 6218 Bearings
622010018034Shop All 6220 Bearings
622211020038Shop All 6222 Bearings
6300103511Shop All 6300 Bearings
6301123712Shop All 6301 Bearings
6302154213Shop All 6302 Bearings
6303174714Shop All 6303 Bearings
6304205215Shop All 6304 Bearings
6305256217Shop All 6305 Bearings
6306307219Shop All 6306 Bearings
6307358021Shop All 6307 Bearings
6308409023Shop All 6308 Bearings
63094510025Shop All 6309 Bearings
63105011027Shop All 6310 Bearings
63115512029Shop All 6311 Bearings
63126013031Shop All 6312 Bearings
63136514033Shop All 6313 Bearings
63147015035Shop All 6314 Bearings
63157516037Shop All 6315 Bearings
63168017039Shop All 6316 Bearings
63178518041Shop All 6317 Bearings
63189019043Shop All 6318 Bearings
63199520045Shop All 6319 Bearings
632010021547Shop All 6320 Bearings
632412026055Shop All 6324 Bearings
680010195Shop All 6800 Bearings
680112215Shop All 6801 Bearings
680215245Shop All 6802 Bearings
680317265Shop All 6803 Bearings
680420327Shop All 6804 Bearings
680525377Shop All 6805 Bearings

Self Aligning Ball Bearing Measurements

Single Row Angular Contact Ball Bearing Measurements

Double Row Angular Contact Ball Bearing Measurements

Size
Inner Dimension (mm)
Outer Dimension (mm)
Width (mm)
3200103014Shop All 3200 Bearings
3201123215.9Shop All 3201 Bearings
3202153515.9Shop All 3202 Bearings
3203174017.5Shop All 3203 Bearings
3204204720.6Shop All 3204 Bearings
3205255220.6Shop All 3205 Bearings
3206306223.8Shop All 3206 Bearings
3207357227Shop All 3207 Bearings
3208408030.2Shop All 3208 Bearings
3209458530.2Shop All 3209 Bearings
3210509030.2Shop All 3210 Bearings
3304205222.2Shop All 3304 Bearings
3305256225.4Shop All 3305 Bearings
3306307230.2Shop All 3306 Bearings
3307358034.9Shop All 3307 Bearings
3308409036.5Shop All 3308 Bearings

Summary

In conclusion, mastering the art of measuring ball bearings and understanding bearing codes is vital for anyone involved in mechanical or industrial applications. By following the steps outlined in this guide, you can confidently and accurately determine crucial parameters like inner and outer diameters, width, and radial play.

Furthermore, decoding bearing designations enables you to select the right bearing for your specific needs, optimizing performance and longevity. Remember that precision is paramount, and a well-measured bearing is essential for efficient machinery and reliable operation.

Malcolm Watson Image

Reviewed by Malcom Watson (Technical Product Engineer for RS Group)

I have over 40 years of experience in Mechanical Power Transmission specialising in Bearings (covering Technical roles and Product Management). I am always motivated to learn more as new bearing innovations are regularly introduced to the market by our leading brands offering even better solutions to customers. Improving downtime and increasing efficiency. Keeping industry moving!

Further Reading

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