Bearing Grease Quantity
Grease to add when relubricating a bearing from the side: G = 0.005 x D x B from outside diameter and width, in grams and oz. Enter mm, inch or a model.
Grease to add, relubricating from the side
16.8 g 0.59 oz
G = 0.005 x 140 x 24 = 16.8 g
Through holes in the ring instead: 0.002 x 140 x 24 = 6.72 g
Replenishment amount per regreasing, not the first fill. Sealed 2RS and ZZ bearings usually do not need regreasing.
The calculator above gives the bearing grease quantity to add each time you relubricate an open bearing from the side. SKF’s formula is G = 0.005 x D x B, with G in grams, D the outside diameter and B the width in millimetres [1]. It is a replenishment amount for bearings that are regreased in service. The first fill of a new bearing or housing is worked out differently, and sealed bearings in normal use usually do not need regreasing.
The formula: G = 0.005 x D x B
| Symbol | Meaning | Unit |
|---|---|---|
| G | Grease to add at each relubrication | g |
| D | Outside diameter of the bearing | mm |
| B | Width of the bearing | mm |
For tapered roller bearings, use the total width T as B; for thrust bearings, the height H [1]. The factor 0.005 applies when the grease goes in from the side of the bearing. When it goes in through holes in the centre of the inner or outer ring, SKF uses 0.002 x D x B instead [1]. The calculator shows both figures.
Inch sizes are converted at 1 in = 25.4 mm before multiplying, and grams are converted to ounces at 1 oz = 28.35 g. D and B are the dimensions of the bearing itself. In a pillow block unit or any other housing, measure or look up the bearing, not the housing.
Worked example: 6018 deep groove ball bearing
| Step | Value |
|---|---|
| Outside diameter D | 140 mm |
| Width B | 24 mm |
| Side relubrication, 0.005 x 140 x 24 | 16.8 g, about 17 g |
| In ounces, 16.8 / 28.35 | 0.59 oz |
| Through holes in the ring, 0.002 x 140 x 24 | 6.72 g |
The dimensions are those on the 6018 bearing page. The same size is the case in our bearing lubrication guide, where the question was the factory grease fill of a sealed 6018-2RS. That is a first-fill decision made at assembly, not a relubrication amount, which is the difference the next two sections cover.
When the formula applies
- Open bearings in a housing with a grease fitting, regreased in service.
- Each regreasing: the result is the amount per relubrication, not a total for the bearing’s life.
- Grease added from the side (0.005) or through holes in the ring (0.002) [1].
When it does not apply
- Sealed and shielded bearings (2RS, ZZ). SKF describes its bearings capped on both sides as lubricated for the life of the bearing and virtually maintenance-free [4]. In normal use they usually do not need regreasing, so there is no relubrication amount to work out; the grease and the fill are set when the bearing is made.
- The first fill. SKF notes that the free volume in a bearing is commonly filled completely at installation, while the housing is only partly filled. With relubrication from the side, it puts the initial housing fill at 40% of the housing’s free volume, and at 20% when relubrication is through holes in the ring [1]. This calculator does not work out that volume.
- Insert bearings in mounted units. They are not in the model list. The inner ring of an insert is wider than the outer ring (a UC205 is 34.1 mm across the inner ring and 17 mm across the outer), and the formula source names only one bearing width [1]. Follow the regreasing instructions for the unit, or send us the model.
Adjust for speed, temperature, water and dirt
The formula gives the same amount for a given size whatever the duty. The operating conditions come in through how often you regrease and how full the housing is kept.
- How often. SKF says a bearing has to be relubricated when the grease life is shorter than the bearing life or when the grease becomes contaminated. Grease life depends mainly on bearing type and size, grease type, speed, load and operating temperature [2].
- Heat, vertical shafts, vibration, contamination. SKF shortens the relubrication interval for higher operating temperatures, bearings on a vertical shaft, high vibration and contamination [2].
- High speed. NSK fills 1/2 to 2/3 of the housing’s free space when the bearing runs at 50% of its limiting speed or less, and 1/3 to 1/2 when it runs faster [3]. The faster the bearing, the less grease the housing takes.
- Slow bearings exposed to dirt and moisture. Where bearings run at very low speeds and need good protection against contaminants and corrosion, SKF recommends filling 70% to 100% of the housing with grease [1].
- Running-in. During running-in, excess grease distributes or escapes, and the operating temperature drops once it has been distributed [1].
About the model list
The list fills in D and B from our dimension records for deep groove ball bearings, tapered roller bearings and spherical roller bearings, the same figures as on each model page. For tapered roller bearings it uses the total width T, as the formula source specifies [1]. Sealed versions such as 6018-2RS have the same dimensions but leave the factory greased, so the result applies only to the open bearing.
For sealed bearings going into a known machine, put the speed, the environment and the maintenance plan on the order; the lubrication guide lists what to include.
Sources
- https://www.skf.com/us/products/rolling-bearings/principles-of-rolling-bearing-selection/bearing-selection-process/lubrication/determining-grease-quantities
- https://www.skf.com/us/products/rolling-bearings/principles-of-rolling-bearing-selection/bearing-selection-process/lubrication/grease-life-and-relubrication
- https://www.nsk.com/tools-resources/abc-bearings/grease-lubrication/
- https://www.skf.com/group/products/rolling-bearings/ball-bearings/deep-groove-ball-bearings/single-row-deep-groove-ball-bearings
FAQ
How much grease should I put in a bearing?
It depends on whether it is the first fill or a relubrication. For relubrication from the side, SKF gives 0.005 x D x B grams, with D the outside diameter and B the width in millimetres; through holes in the ring it is 0.002 x D x B. At installation the free space in an open bearing is commonly filled completely and the housing only partly.
How do I convert the bearing grease quantity to ounces?
Work it out in grams and divide by 28.35. A 6018 bearing, 140 mm outside diameter and 24 mm wide, takes 16.8 g from the side, which is about 0.59 oz.
Do 2RS or ZZ bearings need regreasing?
Usually not. SKF describes its bearings capped on both sides as lubricated for the life of the bearing and virtually maintenance-free, so this calculator does not apply to them. Their grease and fill are set when they are made.
What is the grease amount for a pillow block bearing?
Use the outside diameter and width of the bearing inside the housing, not the size of the housing. Insert bearings have an inner ring wider than the outer ring and the formula names only one width, so for those units follow the regreasing instructions for the unit or send us the model.
How often should a bearing be regreased?
The calculator gives the amount, not the interval. SKF ties the interval to grease life, which depends on bearing type and size, grease type, speed, load and operating temperature, and shortens it for high temperature, a vertical shaft, high vibration and contamination.