Bearing Size Input Form
Use the fields below to estimate a practical bearing size for common rotating shafts, rollers, carts, hobby machines, and household tools.
Example Data Table
This sample shows how the calculator behaves with typical shaft and load combinations.
| Case | Shaft (mm) | Radial Load (N) | Axial Load (N) | RPM | Life (hours) | Suggested Bearing |
|---|---|---|---|---|---|---|
| Small fan shaft | 12 | 350 | 40 | 1450 | 8000 | 6201 |
| Utility cart wheel | 20 | 1200 | 80 | 220 | 5000 | 6204 |
| Workbench roller | 25 | 1600 | 160 | 600 | 10000 | 6205 |
| Light spindle | 30 | 2400 | 500 | 1200 | 12000 | 7206 |
Formula Used
1) Equivalent dynamic load: P = (X × Fr + Y × Fa) × service factor
Fr is radial load, Fa is axial load, and X and Y depend on bearing style and load ratio.
2) Life in million revolutions: L10 = (hours × 60 × RPM) / 1,000,000
3) Required dynamic capacity: C = P × (L10)^(1/p)
For ball bearings, p = 3. For roller bearings, p = 10/3.
4) Estimated bore need: Estimated bore = shaft diameter + fit allowance
5) Static check: the calculator compares a simplified equivalent static load with the selected bearing static rating to show reserve strength.
How to Use This Calculator
- Enter the shaft diameter in millimeters.
- Add the expected radial load and any axial load.
- Provide rotational speed and desired operating life.
- Choose a service factor for light, normal, or rough use.
- Select the bearing style that matches the application.
- Click the calculate button to see the result above the form.
- Review the suggested code, dimensions, safety ratios, and chart.
- Download the result as CSV or PDF if needed.
Frequently Asked Questions
1. What does this bearing size calculator estimate?
It estimates a practical bearing bore, suggested standard bearing code, dynamic capacity need, and reserve safety ratios using shaft size, load, speed, and life inputs.
2. Is the recommendation a final engineering approval?
No. It is a sizing guide for quick selection. Final bearing choice should still consider seals, lubrication, housing fit, temperature, contamination, and manufacturer catalog data.
3. Why do axial loads matter?
Axial force can change equivalent bearing load significantly. Even modest thrust may push a deep groove option toward angular contact or tapered styles.
4. What is the service factor used for?
Service factor increases the effective design load. It helps account for shock, rough starts, uneven surfaces, vibration, and uncertain real-world operating conditions.
5. When should I choose tapered roller bearings?
Tapered roller bearings are useful when loads are heavier and thrust support matters. They often suit wheels, hubs, and stronger combined-load applications.
6. Does a larger outside diameter always mean better?
Not always. Bigger bearings may carry more load, but space, friction, housing size, cost, and speed limits must still match the application properly.
7. What if my shaft diameter falls between standard sizes?
Use the next suitable standard bore or redesign the fit. Avoid forcing a loose mismatch because fit quality affects durability, noise, and alignment.
8. Can I use this for bikes, carts, tools, or hobby machines?
Yes. It is useful for everyday rotating parts like carts, rollers, hobby shafts, small machines, and utility tools needing quick bearing size checks.