Bearing Grease Quantity and Relubrication Interval Calculator

1. Confirm the bearing is grease-lubricated and not sealed for life; obtain bore d, outside diameter D, and width B in mm.
2. Enter maximum continuous speed in rpm, select a published Kf matching the bearing design, and enter sustained grease temperature.
3. Enter positive P/C; select orientation, contamination control, and operating pattern.
4. Enter operating hours/day. Include housing grease only from measured free volume, density, and approved fill percent; use zero volume when unknown.
5. Select Calculate to update the result. Select Reset to restore the worked example.
6. Read initial charge and corrected interval first, then review replenishment, daily feed, base interval, and all factors.
7. Correct red input warnings. Treat yellow warnings as a requirement for OEM, bearing, or grease-supplier review.
8. Do not use for sealed-for-life bearings, oil/solid lubrication, blocked purge paths, lubricator pressure sizing, or safety-critical dosing.

d_m = (d + D)/2

G_p = 0.005DB

G_h = ρV_hφ/100; G_initial = G_p + G_h

t_b = K_f[14,000,000/(n√d_m) − 4d_m]

F_T = 1 for T ≤ 70 °C; otherwise 2^{−((T−70)/15)}

F_L = 1.0, 0.8, 0.6, or 0.4 for P/C bands ≤0.05, ≤0.10, ≤0.15, or above 0.15.

F_O = 1.0 horizontal or 0.5 vertical; F_C = 1.0 clean, 0.5 moderate, or 0.25 severe; F_D = 1.0 continuous or 0.8 intermittent.

t_c = t_bF_TF_LF_OF_CF_D; q_h = G_p/t_c; q_day = q_hh_op

Operating time h_op is the entered operating hours per day, in h/day. It is not an additional correction factor: multiplying the average hourly feed q_h (g/h) by h_op gives the daily feed q_day (g/day).

Lengths are mm, speed is rpm, intervals are hours, and grease mass is g. Kf, factors, and P/C are dimensionless. Load is a positive magnitude; no force sign convention applies. The base interval must be positive. The 0.005DB relation estimates replenishment, not cavity volume.

Reset restores d = 50 mm, D = 100 mm, B = 20 mm, n = 1500 rpm, Kf = 1, T = 90 °C and P/C = 0.08. With a horizontal shaft, moderate contamination, intermittent operation and 8 h/day, the base interval is about 778 h and the corrected interval is about 99 h. Replenishment is 10 g/event and average feed is about 0.81 g/day. Housing volume 250 cm³, density 0.90 g/cm³ and fill 33% add 74.25 g, giving an initial planned charge of 84.25 g. Review each correction and the available purge path with the supplier.

Assumes a conventional grease-lubricated rolling bearing, compatible top-up grease, a usable purge path, and operation within grease and bearing limits. Transparent load, orientation, contamination, and duty factors are conservative planning screens rather than a standard or product approval.

Confirm free space, cage design, speed, temperature, load, grease compatibility, and interval with the OEM and grease supplier. High temperature, high speed, vibration, water, aggressive contamination, or unusual geometry requires product-specific review and field adjustment.

References: SKF bearing lubrication guidance; SKF Lubrication Planner; Timken Grease Lubrication Calculator; and Noria lubrication calculators.