Bearing Life Calculator
Estimate how long a rolling-element bearing will last under a given load and speed. Use it when selecting bearings for motors, gearboxes, or any rotating machinery to meet a target service life.
About this calculator
Bearing fatigue life is expressed as L10 life — the number of operating hours that 90% of a batch of identical bearings will survive. The ISO 281 formula relates life to the ratio of the dynamic load rating C to the applied load P: L10 (in millions of revolutions) = (C / P)³ × 10⁶. To convert to hours, divide by the shaft speed in rpm multiplied by 60: L10h = (C / P)³ × 10⁶ / (n × 60). The exponent is 3 for ball bearings and 10/3 for roller bearings. A higher C/P ratio dramatically extends life — doubling the ratio increases life eightfold. Engineers use this calculation during the design phase to confirm that selected bearings will meet maintenance intervals.
How to use
Suppose a deep-groove ball bearing has a dynamic load rating C = 20,000 N, carries an applied radial load P = 5,000 N, and the shaft spins at 1,500 rpm. Step 1 — compute the load ratio: C/P = 20,000 / 5,000 = 4. Step 2 — cube it: 4³ = 64. Step 3 — multiply by 1,000,000: 64 × 1,000,000 = 64,000,000 revolutions. Step 4 — convert to hours: 64,000,000 / (1,500 × 60) = 711 hours L10 life. Enter C, P, and speed into the calculator to get your result instantly.
Frequently asked questions
What does L10 bearing life actually mean in practice?
L10 life is the number of hours or revolutions at which 10% of a large sample of identical bearings would be expected to show fatigue failure — meaning 90% survive beyond that point. It is a statistical reliability figure, not a guarantee for any single bearing. In practice, engineers often target an L10 life well above the required service interval to provide a safety margin. Actual bearing life can exceed L10 significantly if lubrication, alignment, and cleanliness are maintained.
How does applied load affect bearing fatigue life?
Bearing life is extremely sensitive to load because it varies with the cube of the C/P ratio for ball bearings. Reducing the applied load by just 20% can roughly double the expected life. Conversely, overloading a bearing even slightly can slash its service life dramatically. This is why accurate load analysis — including shock and dynamic loads — is critical when sizing bearings for a machine.
When should I use the L10h formula instead of just the catalogue life rating?
Catalogue ratings state the basic load rating C at a standard reference life of one million revolutions, but real applications differ in speed, load, and duty cycle. Use the L10h formula whenever your operating conditions — speed, applied load, or required service hours — differ from the catalogue reference. For critical applications such as turbines or medical equipment, extended life calculations incorporating lubrication and contamination factors (ISO 281 life modification factor aISO) should also be applied.