Calculation reviewed: 4 October 2026 · Engineering Desk Tools
How to use the Bearing life (L10) calculator
Calculate basic rating life L10 in millions of revolutions and operating hours. Start with measurements or documented values for the equipment and reporting period you actually want to assess. The calculator does not fill in a typical installation for you. Its blank fields help keep a demonstration value from being mistaken for your own operating data.
Choose the required options, enter the values in the labelled units and select Calculate. If a field is rejected, check its range and unit before changing it. The result is accompanied by the equation and assumptions so you can decide whether it answers your engineering question.
Inputs and measurement basis
- Bearing type. Ball bearings use an exponent of 3 and roller bearings 10/3.
- Basic dynamic load rating C (kN). Basic dynamic load rating from the bearing catalogue, in kN. The value must be greater than zero.
- Equivalent dynamic bearing load P (kN). Equivalent dynamic load combining radial and axial loads, in kN. The value must be greater than zero.
- Rotational speed (RPM). Shaft speed in revolutions per minute. The value must be greater than zero.
Record the measurement source and operating condition. Retain unrounded values for verification.
Method and interpretation
Basic rating life is the number of revolutions that 90 percent of identical bearings should reach under the stated load. It follows the ratio of the dynamic load rating to the equivalent load, raised to a power of 3 for ball bearings and 10/3 for roller bearings. Because of this power, a modest increase in load shortens life a lot. Dividing by speed converts revolutions to hours.
L10 (million revolutions) = (C / P)^p, with p = 3 for ball bearings and 10/3 for roller bearings. L10h (hours) = L10 × 1,000,000 / (60 × RPM).
L10 is the basic rating life: the life that 90 percent of a group of identical bearings are expected to reach or exceed under ideal conditions (ISO 281). It does not include lubrication quality, contamination, misalignment, temperature or higher reliability requirements. C is on the bearing data sheet. P must combine radial and axial loads with the bearing factors, and C and P must use the same unit.
Worked example
This example does not populate the form. Enter your own installation data.
Calculated result: 2,400 hours L10h. Basic rating life at 90 percent reliability. Use a modified rating life and the supplier method when lubrication, contamination or reliability needs differ from the basic case.
Check the arithmetic independently using the displayed equation. Retain intermediate precision and compare the final value with your equipment documentation.
Quick-reference table
These are illustrative values, not certified ratings or manufacturer data. Use the form for your own conditions.
Common mistakes
Using the static rating C0 instead of the dynamic rating C; using only the radial load when an axial load is also present; mixing kN with N; forgetting that 90 percent reliability means one bearing in ten fails sooner; ignoring lubrication, contamination and temperature. Before relying on the output, check the decimal format, unit scale and source of each value. Recheck unusual results against the formula.
Frequently asked questions
Are the example values used automatically?
No. Inputs remain blank when the tool opens or when you clear them. The worked example and table are reading material below the calculator. Enter the actual values you want to check each time, and label saved reports so their context is not lost.
What does the result mean?
The result is the basic rating life: the time that 90 percent of identical bearings should survive under the stated conditions. A single bearing may fail earlier, and lubrication and contamination can change the real life.
Can I use a zero or a negative value?
The allowed range follows the meaning of each input. A divisor needs a positive value; other fields may allow zero. Check the form labels and error message rather than forcing an invalid value. A rejected input must be corrected before a result can be shown.
Is this a final design or equipment approval?
No. L10 is the basic rating life: the life that 90 percent of a group of identical bearings are expected to reach or exceed under ideal conditions (ISO 281). It does not include lubrication quality, contamination, misalignment, temperature or higher reliability requirements. C is on the bearing data sheet. P must combine radial and axial loads with the bearing factors, and C and P must use the same unit. Use the calculation as support for a checked decision, and review equipment documentation and applicable requirements before changing an installation or operating setting.
How can I save or share a calculation?
Calculate first, then use Copy result or Print report. Some maintenance tools also provide a CSV summary. Reports contain your own entered data, so review them before sharing. You can share the public page URL without including plant records or confidential measurements.
How do I report an unexpected result?
Use the Contact page and include the tool URL, input values, units, expected output and the reference you used. Explain the measurement basis. Exclude confidential information.
Related tools and records
Use related calculations with consistent units, periods and equipment scope.
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