Bearing Load Calculator
Computes the equivalent dynamic load on a bearing by combining radial and axial forces with an application load factor. Use this when selecting bearings or verifying load ratings in rotating machinery.
Last updated: September 2026
Formula below · 2 sources (asme.org, Wikipedia) · Updated Sep 2026
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About this calculator
Bearings carry radial loads (perpendicular to the shaft) and axial loads (along the shaft), but they do not resist them equally, so the two are not combined as a vector. ISO 281 converts them to an equivalent dynamic load P = X·Fr + Y·Fa, with X and Y from the bearing catalogue. For a deep-groove ball bearing, P = Fr when Fa/Fr ≤ e, and P = 0.56·Fr + Y·Fa otherwise, where e (0.19–0.44) and Y (2.30–1.00) depend on the axial load relative to the bearing's static rating C₀. Without C₀, this calculator uses the most conservative ISO values, e = 0.19 and Y = 2.30, so it may overstate P; use the X and Y from your bearing's catalogue for an exact value (angular-contact and tapered bearings have different factors). The result is multiplied by a load (service) factor for shock and vibration, typically 1.0 for smooth operation to 3.0 for heavy shock: P_design = P × load factor. Compare it with the bearing's dynamic load rating C to estimate life.
How to use
A deep-groove ball bearing carries a radial load of 800 N and an axial load of 600 N, with a moderate shock load factor of 1.5. Step 1 – Fa/Fr = 600/800 = 0.75, above 0.19, so P = 0.56 × 800 + 2.30 × 600 = 448 + 1,380 = 1,828 N (a vector sum, 1,000 N, would understate it). Step 2 – Apply the load factor: 1,828 × 1.5 = 2,742 N. Compare this with the bearing's dynamic load rating. With a small axial load, for example Fr = 1,000 N and Fa = 150 N (Fa/Fr = 0.15), P is simply the radial load, 1,000 N × 1.5 = 1,500 N.
Frequently asked questions
What is the difference between radial load and axial load on a bearing?
Radial load acts perpendicular to the shaft axis, like the weight of a gear or pulley pressing down on the shaft. Axial load (also called thrust load) acts parallel to the shaft axis, such as the force generated by helical gears or a propeller. Most rolling-element bearings can handle both types, but their relative magnitudes determine which bearing type — deep-groove ball, angular contact, or tapered roller — is most appropriate.
How do I choose the correct load factor for my bearing application?
Load factors are selected based on the operating conditions of the machine. A value of 1.0 applies to smooth, vibration-free operation such as precision instruments. Values of 1.2–1.5 suit normal electric motors and pumps with moderate shock. Heavy machinery with frequent shock loads, like crushers or hoists, requires factors of 2.0–3.0 or higher. Always consult the bearing manufacturer's application guidelines or ISO 281 for validated factors specific to your industry.
Why is the Pythagorean theorem used to combine radial and axial bearing loads?
Radial and axial loads are perpendicular, but a rolling bearing does not resist them equally: an axial load shifts the load onto fewer balls and changes the contact angle. That is why ISO 281 uses P = X·Fr + Y·Fa with bearing-specific factors instead of the vector sum √(Fr² + Fa²); for a deep-groove ball bearing with significant thrust, the vector sum can understate P by 30% or more and overstate life by a factor of two or more. This calculator applies the conservative deep-groove factors (X = 0.56, Y = 2.30 when Fa/Fr > 0.19).