How to Identify the Right Ball Bearing Size for Your Application

Selecting the correct ball bearing size is essential to ensure smooth operation, longer equipment life, and cost efficiency. Whether you’re working with industrial machinery, electric motors, automotive components, or agricultural equipment, choosing the wrong bearing can lead to premature failure and expensive downtime.

In this guide, we’ll explain how to

identify the right ball bearing size for your specific application, step by step.

🧩 Why Bearing Size Matters

Ball bearings support radial and axial loads, reduce friction, and ensure rotating parts function efficiently. An incorrect bearing size can result in:

• Excessive wear and tear

• Overheating or vibration

• Misalignment or shaft damage

• Frequent replacements and higher costs

📏 Key Bearing Dimensions You Must Know

Each ball bearing has three core dimensions, usually represented in millimeters (mm):

Dimension	Description
Bore Diameter (d)	Inner hole size that fits on the shaft
Outer Diameter (D)	Total width across the bearing’s outside
Width (B)	Thickness of the bearing

Example: 6205 bearing

• Bore (d) = 25 mm

• Outer Diameter (D) = 52 mm

• Width (B) = 15 mm

🧠 Step-by-Step Guide to Choosing the Right Bearing Size

1. Measure the Shaft Diameter (Bore)

Use a vernier caliper to measure the diameter of the shaft where the bearing will be installed. This gives you the bore size (d).

2. Determine the Housing Size

Measure the inside diameter of the bearing housing (outer ring seat). This helps define the outer diameter (D) of the bearing.

3. Check the Bearing Width

The bearing should fit comfortably within the housing or machine slot without sticking out or getting compressed. This gives you the width (B).

4. Understand Load and Speed Requirements

• High-speed machines: Require precision bearings (like 6xxx or 7xxx series)

• Heavy load applications: Need thicker and stronger bearings (like 63xx series)

• Axial loads: May require angular contact or thrust bearings

5. Match the Series Type

Common ball bearing series:

• 6000 Series – Light-duty, high-speed

• 6200 Series – Medium-duty, versatile

• 6300 Series – Heavy-duty, larger loads

6. Consider Fitment and Tolerance

Check the ISO fit tolerance (shaft vs. bore) to ensure proper interference or clearance fit.

🔍 Using Bearing Number to Identify Size

Bearing numbers follow a standard pattern:

Example: 6203 2RS

• 6 → Type (single row deep groove)

• 2 → Series (medium)

• 03 → Bore = 17 mm (multiply last 2 digits by 5 if >04)

• 2RS → Rubber sealed on both sides

📘 Bore Conversion Table:

Code	Bore (mm)
00	10
01	12
02	15
03	17
04	20
05	25

🛠️ Tools to Help You Select Bearing Size

• Bearing Caliper or Digital Vernier

• Bearing Catalog (SKF, NTN, FAG, etc.)

• Online Bearing Size Finder Tools

• Manufacturer Datasheets or Engineering Drawings

🗺️ Geographic & Industry Use Cases

Region/Condition	Recommended Bearing Series
High-speed motors (urban factories)	6000, 6200 ZZ/2RS
Dusty/rural/agriculture areas	6200 or 6300 series 2RS
Heavy industrial machinery	6300 series, with C3 clearance
Compact space (appliances)	Miniature series (608, 609, etc.)

✅ Conclusion: Checklist for Identifying Right Bearing

Size

✔ Measure shaft diameter (bore)✔ Measure housing or casing (outer diameter)✔ Check required bearing width✔ Consider application load & speed✔ Decode bearing number if available✔ Choose correct sealing type (ZZ or 2RS)✔ Cross-check with manufacturer or expert

🔗 Need Help Sizing Your Bearing?

At IGHBearing.com, we offer a wide range of ball bearings with expert support to help you choose the right one. Whether you need standard sizes, custom orders, or bulk deals, we’ve got you covered.

👉 Explore Our Bearing Size Chart | 📞 Contact Our Support Team