Bearing size is normally identified by three dimensions: ID, OD, and width. ID is the bore size that fits the shaft. OD is the outside diameter that fits the housing or wheel. Width is the bearing thickness. A bearing size chart helps buyers compare metric and inch bearings, but the chart should be used with the full bearing number, seal type, clearance, material, and application details before ordering.
For most deep groove ball bearings, a dimension match is only the starting point. Two bearings can share the same ID, OD, and width but differ in shields, seals, grease, internal clearance, material, cage, and precision level. That is why a useful size guide should help you read dimensions and also prepare the information needed for a reliable RFQ.
What ID, OD, and Width Mean
Bearing dimensions are usually written as ID x OD x width. For example, a metric bearing may be described by bore diameter, outside diameter, and width in millimeters. Inch series bearings use inch dimensions, but the same three-dimensional logic applies.
| Dimension | What It Means | What to Check |
|---|---|---|
| ID | Inside diameter or bore | Shaft diameter, fit, and whether the bearing slides or presses on. |
| OD | Outside diameter | Housing bore, wheel bore, pulley bore, or outer seat. |
| Width | Bearing thickness | Available space, spacers, shoulder position, and retaining parts. |
| Chamfer | Edge relief at ring corners | Shaft and housing shoulder clearance. |
| Closure width effect | Seal or shield package | Nearby washers, spacers, and snap features must not rub. |
When measuring a used bearing, clean the part first. Dirt, burrs, rust, and worn edges can make a caliper reading misleading. If the bearing is damaged, measure the shaft and housing as well, not only the removed bearing.
Metric and Inch Bearing Sizes
Metric bearings are common in motors, pumps, conveyors, automation equipment, and general machinery. Inch bearings are common in some older equipment, North American replacement applications, hobby equipment, and compact specialty designs.
For metric ball bearings, common bore and series families include 6000, 6200, 6300, 6800, and 6900 series. Thin-section series such as 6800 and 6900 save radial space. Wider series such as 6200 or 6300 often provide more capacity within the same bore range.
For inch sizes, buyers should confirm the exact fractional or decimal dimension. A small difference between 1/4 in and a nearby metric bore can create poor fit, slip, heat, or installation damage. If you need compact inch bearings, review miniature inch series bearings by measured ID, OD, and width instead of guessing from appearance.
Common Bearing Series and What They Suggest
A bearing number often gives clues about size family and section. It does not tell the full story, but it helps narrow the search.
| Series or Type | Common Use | Size Selection Note |
|---|---|---|
| 6000 series | Compact general use | Good where space is limited and loads are moderate. |
| 6200 series | General motors and machinery | Often a balanced choice for many radial-load positions. |
| 6300 series | Heavier general use | Wider and larger than 6200 for the same bore range. |
| 6800 / 6900 series | Thin-section positions | Useful when OD or width is limited. |
| Flanged miniature bearings | Small guides, rollers, and instruments | Confirm flange OD and flange thickness, not only bearing OD. |
| Stainless sizes | Wet or corrosion-risk areas | Match size plus material, seal, and lubricant needs. |
For buyers working from a miniature flange part, the flange matters. A plain bearing with the same ID, OD, and width may not replace a flanged version because the flange locates the part axially. CXE Bearing also provides a flanged miniature ball bearing size chart for small flanged formats.
Why Size Alone Is Not Enough
A bearing size chart can tell you what may fit. It cannot confirm whether the bearing will last in the machine.
The same size may be available as open, ZZ, 2RS, stainless, chrome bearing steel, low-noise, C3 clearance, or higher precision. A clean electric motor may need a different closure and grease than an outdoor roller. A wet packaging machine may need stainless steel bearings or a corrosion-resistant arrangement. A standard replacement may use metric ball bearings with a specific closure and clearance.
Before approving a substitute, compare:
- bearing number and suffix
- ID, OD, and width
- open, shielded, or sealed construction
- clearance such as C0 or C3
- material
- grease or lubrication method
- shaft and housing condition
- RPM, load direction, and environment
Common Mistakes
- Measuring only the outside diameter and ignoring ID or width.
- Replacing a flanged bearing with a plain bearing because the bore matches.
- Treating inch and metric sizes as interchangeable when they are only close.
- Ignoring suffixes such as ZZ, 2RS, C3, P6, or material codes.
- Measuring a worn bearing but not checking the shaft and housing.
- Choosing by size only when the real issue is load, contamination, speed, or lubrication.
- Ordering a stainless bearing without confirming seal, grease, and application environment.
RFQ Checklist
Send these details when requesting a quote:
- bearing number, if known
- ID, OD, and width
- metric or inch dimensions
- closure type: open, ZZ, 2RS, or other
- material requirement
- clearance requirement such as C0, C2, C3, or C4
- precision requirement such as P0, P6, or ABEC grade if specified by the machine
- quantity by model
- application and equipment position
- RPM and load direction if known
- operating environment: dust, moisture, washdown, heat, or clean indoor use
- packaging preference for resale, repair stock, or factory assembly
If you are comparing load capacity as well as dimensions, review the static vs dynamic load rating guide before choosing a smaller or thinner bearing.
FAQ
What are the three main bearing dimensions?
The three main dimensions are ID, OD, and width. ID fits the shaft, OD fits the housing or outer seat, and width controls how much axial space the bearing occupies.
Can I replace a bearing if the dimensions match?
Not always. The dimensions may match while the seal type, clearance, material, cage, grease, or precision level is different. Those details can change heat, noise, friction, corrosion resistance, and service life.
Are metric and inch bearings interchangeable?
Only when the measured dimensions and application requirements truly match. Near-size substitutions can create loose fit, tight fit, noise, heat, or early failure.
What does bearing width affect?
Width affects available space, shaft shoulders, spacers, retaining rings, and load capacity. A wider or narrower replacement may not seat correctly even if ID and OD match.
What should I send if I do not know the bearing number?
Send clear measurements for ID, OD, and width, photos of both sides, any markings, the machine position, RPM if known, and whether the bearing is open, shielded, sealed, flanged, stainless, or special.
Get the Right Size Before Ordering
A bearing size chart is useful when it is connected to real operating details. CXE Bearing can help compare measured dimensions with common bearing series, closure options, material choices, and RFQ requirements. Send the bearing number or ID, OD, width, photos, and application details so the replacement can be reviewed before bulk ordering.