What are the X and Y factors?

X is the radial load factor and Y is the axial load factor. They depend on the bearing type and the ratio Fa/Fr relative to the e-value. When Fa/Fr ≤ e, the axial load has negligible effect (X=1, Y=0). When Fa/Fr > e, both X and Y apply.

What is the e-value in bearing calculations?

The e-value is a threshold ratio specific to each bearing type. It determines whether the axial load significantly affects bearing life. When Fa/Fr exceeds e, the Y factor must be applied to account for the axial load contribution.

How do I handle pure radial load?

For pure radial load (Fa = 0), the equivalent load simplifies to P = Fr. No axial factor applies, and you can use the radial load directly in the L10 life calculation.

Can I use this for static equivalent load P0?

This calculator computes the dynamic equivalent load P for life calculations. For static equivalent load P0, the formula is similar but uses different X0 and Y0 factors. Use the Bearing Static Safety Factor calculator for P0 assessment.

Free Engineering Tool #046

Bearing Equivalent Dynamic Load Calculator

Calculate the equivalent dynamic bearing load P = X·F_r + Y·F_a. Automatically selects X,Y factors based on bearing type and F_a/F_r ratio vs. e-value.

P = X·Fr + Y·Fa e-Value Check Auto X,Y Selection

Radial Load F_r (kN)

Axial Load F_a (kN)

Bearing Type

Quick presets

Results

Equivalent Dynamic Load P

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Fa/Fr Ratio

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e-Value Threshold

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Factors Used (X, Y)

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Load Condition

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Equivalent Dynamic Load

The equivalent dynamic bearing load combines radial and axial forces into a single value:

The condition is: if F_a/F_r ≤ e, then P = F_r. If F_a/F_r > e, then P = X·F_r + Y·F_a.

X, Y and e Factors by Bearing Type

Bearing Type	e	X (Fa/Fr ≤ e)	X (Fa/Fr > e)	Y (Fa/Fr > e)
Deep groove ball (DGBB)	0.19	1	0.56	2.30
Angular contact 15°	0.38	1	0.44	1.47
Angular contact 25°	0.68	1	0.41	0.87
Angular contact 40°	1.14	1	0.35	0.57
Self-aligning ball	0.40	1	0.65	1.71
Cylindrical roller	—	1	—	—
Tapered roller	0.37	1	0.40	1.60
Spherical roller	0.27	1	0.67	2.35

ℹ️ Note: The values above are simplified typical values. Exact X, Y, and e values depend on the specific bearing series and the ratio C₀/F_a. Consult manufacturer catalogs for precise values.

Practical Example

Example — Deep Groove Ball Bearing 6208

Given: F_r = 8 kN, F_a = 3 kN

F_a/F_r = 3/8 = 0.375 > e = 0.19 → axial load is significant

P = 0.56 × 8 + 2.30 × 3 = 4.48 + 6.90 = 11.38 kN

The equivalent dynamic load P is a hypothetical constant radial load that would give the same bearing life as the actual combined radial and axial loads. It is calculated as P = X·F_r + Y·F_a.

X is the radial load factor and Y is the axial load factor. When F_a/F_r ≤ e, the axial load has negligible effect (X=1, Y=0). When F_a/F_r > e, both X and Y apply to account for the combined loading.

The e-value is a threshold ratio specific to each bearing type. It determines whether the axial load significantly affects bearing life. Different bearing types have different e-values based on their internal geometry and contact angle.

For pure radial load (F_a = 0), the equivalent load simplifies to P = F_r. No axial factor applies since F_a/F_r = 0, which is always ≤ e.

This calculator computes the dynamic equivalent load P for L₁₀ life calculations. For the static equivalent load P₀, the formula is similar but uses different X₀ and Y₀ factors. Use the Bearing Static Safety Factor calculator for P₀ assessment.

The procedures described on this page were developed and field-tested by the Vibromera team using the Balanset-1A, a portable dual-channel balancer and vibration analyzer for on-site rotor balancing.