# Bearing L10 Life Calculator (ISO 281 Basic Rating Life) > Source: https://netray.co/tools/bearing-l10-life-calculator-iso-281 > Publisher: Netray (netray.co), AI and integration engineering for ERP and manufacturing systems. > Section: Free Tools ## Short answer Basic and adjusted rating life of ball and roller bearings from C, P and rpm, with a load sweep chart. ## Category maintenance ## Industry Manufacturing ## Audience - Reliability engineer - Maintenance engineer - Mechanical designer ## Tool **Kind:** calculator **Inputs:** #### Basic dynamic load rating C **Key:** c_rating **Type:** number **Default:** 30 **Min:** 0.1 **Step:** 0.5 **Unit:** kN **Help:** From the bearing catalogue or datasheet. #### Equivalent dynamic load P **Key:** p_load **Type:** number **Default:** 5 **Min:** 0.1 **Step:** 0.1 **Unit:** kN **Help:** Combined radial and axial load converted to one equivalent value. #### Shaft speed **Key:** rpm **Type:** number **Default:** 1480 **Min:** 1 **Step:** 10 **Unit:** rpm #### Bearing type **Key:** exponent **Type:** select **Default:** 3 **Options:** ##### Ball bearing (p = 3) **Value:** 3 ##### Roller bearing (p = 10/3) **Value:** 3.3333333 #### Reliability factor a1 **Key:** a1 **Type:** select **Default:** 1 **Options:** ##### 90% (L10), a1 = 1 **Value:** 1 ##### 95% (L5), a1 = 0.64 **Value:** 0.64 ##### 96% (L4), a1 = 0.55 **Value:** 0.55 ##### 97% (L3), a1 = 0.47 **Value:** 0.47 ##### 98% (L2), a1 = 0.37 **Value:** 0.37 ##### 99% (L1), a1 = 0.25 **Value:** 0.25 #### Operating hours per year **Key:** hours_year **Type:** number **Default:** 6000 **Min:** 1 **Max:** 8760 **Step:** 100 **Unit:** h **Outputs:** #### Load ratio C / P **Key:** load_ratio **Expr:** c_rating / p_load **Format:** decimal #### Rating life **Key:** l10_mrev **Expr:** a1 * pow(c_rating / p_load, exponent) **Format:** decimal **Description:** Million revolutions at the chosen reliability. #### Rating life in hours **Key:** l10_hours **Expr:** l10_mrev * 1000000 / (60 * rpm) **Format:** integer **Primary:** true **Description:** Operating hours before 10% (or chosen %) of a large group would show fatigue. #### Rating life in years **Key:** l10_years **Expr:** l10_hours / hours_year **Format:** decimal **Primary:** true **Chart:** #### Rating life (hours) vs equivalent load **Type:** line **X:** p_load **From:** 1 **To:** 20 **Steps:** 30 **Series:** - l10_hours **Disclaimer:** Basic rating life only. It ignores lubrication film, contamination and misalignment (the ISO 281 a_ISO modifier). Use the bearing maker's tool for final design decisions. ## Content **Intro:** The L10 life of a rolling bearing is the number of revolutions that 90% of a large group of identical bearings reach before fatigue spalling appears. Enter C, P and speed to get life in hours and years, and see how life collapses as load rises. **Sections:** #### How to use the calculator **Body:** Take the basic dynamic load rating C from the bearing datasheet and compute the equivalent dynamic load P from your radial and axial forces using the X and Y factors in the catalogue. Enter shaft speed, choose ball or roller exponent, and pick the reliability you need. The result is shown in million revolutions, operating hours and calendar years at your duty cycle. The chart sweeps P so you can see the sensitivity of life to load. #### The formula behind it **Body:** The basic rating life is L10 = (C / P) to the power p, in million revolutions, with p = 3 for ball bearings and 10/3 for roller bearings. Hours follow from L10h = L10 x 1,000,000 / (60 x n) with n in rpm. The reliability factor a1 scales life for survival probabilities above 90%. Because of the exponent, a 20% increase in load cuts life by roughly 40% on a ball bearing. **Bullets:** - Life falls with the cube of load for ball bearings - Doubling speed halves life in hours but not in revolutions - a1 = 1 corresponds to the familiar L10 definition #### Reading the result and common mistakes **Body:** A computed life is a statistical figure, not a guarantee. Many field failures happen far earlier because of contamination, poor lubrication, misalignment or electrical fluting, none of which appear in basic rating life. Use L10 to compare design options and to set a plausible replacement or inspection horizon, then let condition monitoring tell you when an individual bearing is actually degrading. **Bullets:** - Using the static rating C0 instead of the dynamic rating C - Forgetting to convert axial load into equivalent load P - Mixing kN and N between C and P - Treating a 30-year computed life as proof that bearings will not fail **Cta:** Netray can pull running hours and failure history from your ERP maintenance module so measured bearing life can be compared against these calculated figures. **Faq:** #### What does L10 mean? **Answer:** L10 is the life that 90% of a large group of identical bearings, run under the same conditions, will reach or exceed before the first sign of material fatigue. Ten percent are expected to fail sooner. #### Why is the exponent 3 for ball bearings? **Answer:** It comes from the empirical relationship between load and fatigue life of point-contact bearings. Roller bearings have line contact, which gives a slightly higher exponent of 10/3. #### Is L10h the same as time to failure? **Answer:** No. It is a statistical rating life for a group. Individual bearings can fail much earlier or last several times longer, and real life depends on lubrication, cleanliness and alignment. #### How do I get P if I have radial and axial loads? **Answer:** Use P = X Fr + Y Fa with the X and Y factors listed in the bearing catalogue for your bearing type and the ratio Fa / Fr. For pure radial load on many bearings, P equals Fr. ## Search terms bearing L10 life calculator, bearing life calculation formula, ISO 281 rating life, basic rating life bearing, bearing life hours calculator, dynamic load rating C over P, L10h bearing life, bearing replacement interval --- Talk to an engineer: https://netray.co/contact?intent=erp_ai | Machine catalog: https://netray.co/agent/catalog.json