This Bearing Equivalent Load + Dynamic Capacity spreadsheet from 3D-LABS follows ISO standards and gives instant, checkable results for practising engineers — no manual derivation required.
This spreadsheet calculates the equivalent dynamic bearing load P from combined radial and axial forces per ISO 281:2007 and ISO 76:2006 (static capacity), then determines the minimum required basic dynamic load rating C to achieve a target L10h life — the fundamental bearing specification calculation for all rotating machinery.
What standard does this calculation follow?
ISO 281:2007 (Dynamic load ratings and rating life), ISO 76:2006 (Static load ratings), SKF General Catalogue 6000 EN Section 6 (Load calculation), ABMA Standard 9 (Ball bearings) and ABMA Standard 11 (Roller bearings).
What formula is used?
Equivalent dynamic load: P = XFr + YFa, where X = radial load factor, Y = axial load factor (from ISO 281 bearing-type tables; for a deep-groove ball bearing, Y depends on Fa/Fr ratio and bearing series). Required C = P × (L10h × 60n / 10^6)^(1/p), where p = 3 (ball) or 10/3 (roller).
Frequently Asked Questions
How is equivalent bearing load P calculated per ISO 281?
P = XFr + YFa, where Fr = radial force (kN), Fa = axial force (kN), X = radial factor, Y = axial factor. For a deep-groove ball bearing (e.g., SKF 6312), if Fa/Fr ≤ e: X = 1.0, Y = 0; if Fa/Fr > e: X = 0.56, Y = 1.4 (exact values from ISO 281 Table A.4 or SKF catalogue). e = 0.19–0.57 depending on Fa/C0 ratio.
What is the difference between dynamic load rating C and static load rating C0?
Dynamic rating C (ISO 281): the load causing L10 = 10^6 revolutions (90% survival). Used for rotating bearings. Static rating C0 (ISO 76): maximum load that causes permanent deformation ≤ 0.0001 × rolling element diameter at most stressed contact. Used for bearings under shock loads or static load with very slow rotation (n < 1 rpm).
Does this spreadsheet handle combined radial and axial loads on tapered roller bearings?
Yes. For tapered roller bearings, the equivalent load formula includes an induced axial force component: Fa_induced = Fr × 0.5/Y (from ISO 281 Table A.5). The spreadsheet handles back-to-back (DB) and face-to-face (DF) mounting arrangements, where one bearing’s induced thrust must be reacted by the other, per SKF catalogue Section 10.
What’s Included
An instant Excel download with the complete formula set, a worked numerical example, and reference to the governing standard — ready to adapt to your own project inputs.
