When it comes to machinery, vehicles, and countless mechanical systems, ball bearings play a vital role in reducing friction and ensuring smooth rotational movement. From heavy industrial equipment to everyday household items like fans, roller skates, and bicycles, ball bearings are everywhere. But choosing the right size is critical — too small, and the bearing may fail under load; too large, and it may not fit the application at all.
That’s where a ball bearing size chart comes in handy. It provides engineers, mechanics, and DIY users with precise dimensions — including inner diameter, outer diameter, and width — making it easier to select the correct bearing for any project.
In this guide, we’ll break down:
What ball bearings are and why they matter
The importance of ball bearing sizing
Standard ball bearing sizes and their applications
A detailed ball bearing size chart
How to select the right ball bearing for your project
What is a Ball Bearing?
A ball bearing is a type of rolling-element bearing that uses small hardened steel (or ceramic) balls placed between two rings — the inner race and the outer race. These balls reduce rotational friction and handle both radial and axial loads, making machinery run smoother and more efficiently.
Common types of ball bearings include:
Deep Groove Ball Bearings – used in electric motors, household appliances, and cars.
Angular Contact Bearings – designed for higher axial load applications.
Self-Aligning Bearings – ideal for applications with misalignment issues.
Thrust Ball Bearings – primarily for axial load handling.
Why Ball Bearing Size Matters
The size of a ball bearing directly affects performance, durability, and efficiency. Here’s why correct sizing is crucial:
Load Capacity – A larger bearing can handle more weight and stress.
Speed Limit – Smaller bearings typically allow higher speeds due to less mass and friction.
Fit and Compatibility – The bearing must fit precisely with shafts, housings, and mechanical assemblies.
Longevity – Properly sized bearings reduce wear and prevent premature failure.
Choosing the wrong size could result in overheating, vibration, excessive noise, or even catastrophic equipment damage.
Standard Ball Bearing Dimensions
Every ball bearing is defined by three key measurements:
Inner Diameter (ID) – The size of the hole (bore) that fits onto the shaft.
Outer Diameter (OD) – The total width across the outside of the bearing.
Width (W) – The thickness of the bearing.
Bearings are often identified by a bearing number/code that corresponds to these dimensions. For example, a 6204 bearing has an ID of 20 mm, OD of 47 mm, and W of 14 mm.
Ball Bearing Size Chart
Below is a standard ball bearing size chart with some of the most commonly used bearings across industries:
| Bearing Number | Inner Diameter (ID) | Outer Diameter (OD) | Width (W) | Common Applications |
|---|---|---|---|---|
| 608 | 8 mm | 22 mm | 7 mm | Skateboards, fidget spinners, roller skates |
| 6000 | 10 mm | 26 mm | 8 mm | Small electric motors, pumps |
| 6001 | 12 mm | 28 mm | 8 mm | Automotive parts, power tools |
| 6002 | 15 mm | 32 mm | 9 mm | Fans, compressors |
| 6003 | 17 mm | 35 mm | 10 mm | Agricultural machinery |
| 6203 | 17 mm | 40 mm | 12 mm | Washing machines, alternators |
| 6204 | 20 mm | 47 mm | 14 mm | Industrial motors, conveyors |
| 6205 | 25 mm | 52 mm | 15 mm | Gearboxes, pumps |
| 6206 | 30 mm | 62 mm | 16 mm | Heavy-duty equipment |
| 6306 | 30 mm | 72 mm | 19 mm | Automotive gearboxes |
| 6307 | 35 mm | 80 mm | 21 mm | Mining and construction machinery |
| 6310 | 50 mm | 110 mm | 27 mm | Industrial gearboxes, crushers |
| 6312 | 60 mm | 130 mm | 31 mm | Wind turbines, heavy machinery |
Note: This is a simplified chart. Ball bearings are available in hundreds of sizes and types depending on industry needs.
Ball Bearing Size Chart PDF:
The Ball Bearing Size Chart PDF is a comprehensive guide for engineers, mechanics, and DIY enthusiasts. It includes detailed dimensions such as inner diameter, outer diameter, and width for commonly used ball bearings. This easy-to-use chart helps you quickly select the right bearing for your machinery, vehicles, or projects, ensuring optimal performance, reduced wear, and longer lifespan. Perfect for industrial, automotive, and hobby applications.
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How to Read a Ball Bearing Number
Bearing numbers follow an international coding system. Here’s a quick example:
6204
6 → Type (single row deep groove ball bearing)
2 → Bearing series (capacity and robustness)
04 → Bore size (04 × 5 = 20 mm bore)
This means the 6204 is a deep groove ball bearing with a 20 mm bore.
Applications of Different Ball Bearing Sizes
Different bearing sizes are used in different sectors. Here are a few examples:
Small Bearings (608, 6000 series) – Used in bicycles, skateboards, printers, fans, and hobby tools.
Medium Bearings (6203, 6204, 6205) – Found in washing machines, pumps, automotive alternators, and electric motors.
Large Bearings (6306, 6310, 6312) – Heavy-duty machinery, mining equipment, construction vehicles, and industrial gearboxes.
Tips for Choosing the Right Ball Bearing
Measure the Shaft and Housing – Always confirm the ID and OD match the assembly.
Consider Load Requirements – Higher loads require stronger and larger bearings.
Check Speed Rating – Ensure the bearing can handle the rotational speed of your equipment.
Think About Environment – For dusty, wet, or high-temperature environments, sealed or ceramic bearings may be better.
Lubrication Needs – Some bearings come pre-lubricated, while others require periodic maintenance.
Advantages of Using the Correct Bearing Size
Reduced wear and tear
Longer equipment lifespan
Improved efficiency and performance
Less vibration and noise
Cost savings in maintenance and downtime
Ball Bearing Sizes and Applications
Ball bearings may seem small, but they are at the heart of countless innovations in engineering and everyday life. Imagine a skateboard without its 608 bearings — the wheels would not roll freely, and the rider would struggle with every push. Similarly, think of an automotive alternator running without the precise fit of a 6203 bearing — the result would be overheating, vibrations, and eventual failure of the charging system.
This shows that size is not just a measurement, but a guarantee of performance. For engineers, using a chart ensures the bearing fits perfectly within the shaft and housing, minimizing chances of error. For hobbyists and DIY users, it prevents wasted time and money on the wrong parts.
Specialized Bearing Sizes
In addition to standard bearings, many industries rely on specialized ball bearings:
Miniature Ball Bearings (ID below 10 mm) – These are often used in drones, dental tools, and precision instruments.
Large-Diameter Bearings (OD above 100 mm) – Found in wind turbines, cranes, and industrial presses where massive loads must be managed.
Thin-Section Bearings – Useful when space is limited but strength and smooth motion are still required, such as in robotics or aerospace.
Importance of Material and Design Alongside Size
While size is crucial, material and design also play a big role. Standard ball bearings are made of chrome steel, but for corrosive environments, stainless steel or ceramic bearings are better choices. Similarly, sealed bearings prevent dust and moisture from entering, making them ideal for outdoor applications.
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Conclusion
A ball bearing size chart is more than just numbers — it’s a vital reference tool for engineers, mechanics, and hobbyists. Whether you are working on a skateboard, repairing an industrial motor, or maintaining heavy machinery, selecting the correct size ensures efficiency, durability, and safety.
By understanding bearing numbers, dimensions, and applications, you will always be equipped to choose the right bearing for the job. Keep a size chart handy, and you will save time, money, and frustration in every project.