2026-07-30 9 min
Grease Quantity Calculator
Calculate optimal grease fill quantity for bearings and mechanical components. Proper grease quantity prevents over-greasing (overheating) and under-greasing (starvation).
Calculator
Outer Diameter D (mm)
Width B (mm)
Bearing Type
Speed Factor (n x d_m)
Operating Temperature (°C)
Results
Normal
Grease Fill Quantity
15.0g
Total grease quantity for a full bearing pack
Initial Fill (35%)
5.3g
Recommended initial grease fill (35% of free space)
Relubrication Quantity
3.8g
Grease amount per relubrication event
Relubrication Interval
1000hours
Recommended hours between regreasing
Grease Volume
16.5cm³
Grease volume in cubic centimeters
Visualizations
Results Overview
15gGrease Fill Quantity
5.3gInitial Fill
3.8gRelubrication Quantity
1,000gRelubrication Interval
16.5gGrease Volume
Formula
Grease fill quantity is estimated from bearing dimensions. Q is in grams when D and B are in mm.
Q = D x B x 0.005
Variables
| Symbol | Name | Unit | Description |
|---|---|---|---|
| Q | Grease Fill Quantity | g | Total grease mass for full bearing pack |
| D | Bearing Outer Diameter | mm | Outside diameter of the bearing |
| B | Bearing Width | mm | Width of the bearing |
Explanation
The empirical formula Q = D x B x 0.005 provides a quick estimate of grease quantity based on bearing geometry. The factor 0.005 g/mm includes grease density (approximately 0.9 g/cm) and typical free volume fraction. Initial fill is typically 25-45% of free space, with 35% as the recommended default. Over-filling causes churning, temperature rise, and grease degradation.
Derivation
Bearing free volume is approximately proportional to the bearing envelope volume (p/4 x D x B). Empirical factors from SKF and FAG bearing engineering manuals yield the simplified expression Q = D x B x 0.005 for grease mass in grams when D and B are in millimeters.
Step-by-Step Calculation
Follow each step to understand how the result is calculated from your inputs.
Step 1
Measure or look up the bearing outer diameter D and width B from bearing catalog data.
Outer Diameter D:100.0 mm
Width B:30.0 mm
Result: D = 100.0 mm, B = 30.0 mm
Step 2
Apply the grease quantity formula using bearing dimensions.
Q = D x B x 0.005
D:100.0 mm
B:30.0 mm
Intermediate: Q = 100.0 x 30.0 x 0.005
Result: Q = 15.0 g
Step 3
Determine initial fill (35% of free space for most applications).
Total Q:15.0 g
Intermediate: Initial fill = Q x 0.35
Result: Initial fill = 5.3 g
Final Answer
15.0
Worked Examples
See how the calculator works with different scenarios.
Scenario
A 6208 deep groove ball bearing with D = 80 mm, B = 18 mm, operating at 3000 RPM with speed factor n x d_m = 150,000, temperature 65 C.
Inputs
Bearing Type:Deep Groove Ball
D:80 mm
B:18 mm
Speed Factor:150,000
Temperature:65 C
Calculation
Q = 80 x 18 x 0.005 = 7.2 g total Initial fill (35%) = 7.2 x 0.35 = 2.5 g Relubrication qty (25%) = 7.2 x 0.25 = 1.8 g Interval: base 4000 hrs, adjusted for speed: 4000 x (100000/150000) = 2667 hrs
Result
Initial fill = 2.5 g, Relubrication interval = 2667 hours
Interpretation
The 6208 bearing needs only 2.5 g of grease for initial fill. Over-greasing this common bearing is a frequent cause of overheating in electric motors.
Understanding Your Result
Your Result: Grease Fill Quantity: 15.0 g
Typical range: 25-35% fill (high-speed bearings, n x d_m > 300,000), 30-40% fill (moderate speed, n x d_m 100,000-300,000), 40-50% fill (slow speed, n x d_m < 100,000), 50-70% fill (very slow speed, oscillating, or vertical shafts)
What This Means
Grease quantity (Q) represents the optimal grease mass for bearing lubrication. Under-filling risks starvation and wear; over-filling causes churning, overheating, and premature grease failure.
Why It Matters
Proper grease fill is critical for bearing life. Over 60% of bearing failures are lubrication-related, with incorrect grease quantity being a primary cause. The right fill reduces operating temperature 10-20 C compared to over-packed bearings.
Professional Interpretation
The 35% initial fill rule is conservative for most applications. For high-speed spindles (n x d_m > 500,000), reduce to 20-25%. For slow-speed, large bearings subject to contamination, increase to 40-50%. The relubrication quantity of 25% of the original fill replaces grease that has degraded, migrated, or been expelled.
Recommendations
- •Use the calculated initial fill as a starting point and adjust based on running temperature rise
- •For high-speed applications (>300,000 nd_m), reduce fill to 25% and monitor bearing temperature
- •For vertical shaft bearings, increase fill by 10-15% to compensate for grease migration downward
- •Schedule relubrication at 50% of the calculated interval for critical or hard-to-access bearings
Educational Content
Introduction
Grease is the most common lubricant for rolling element bearings, used in approximately 90% of all bearings. Proper grease quantity is essential for optimal bearing performance, reliability, and service life.
Concept Explanation
Grease consists of a base oil (typically 70-95%), a thickener (5-30%), and additives. The thickener forms a sponge-like structure that holds the base oil. Under rotation, grease is worked and releases oil into the rolling contacts. Too little grease causes starvation; too much causes churning, shear degradation, and temperature rise. The optimal fill balances oil supply with minimal mechanical working.
Applications
▸Electric motor bearing lubrication
▸Industrial fan and pump bearings
▸Conveyor roller bearings
▸Automotive wheel bearings
▸Machine tool spindle bearings
▸Agricultural equipment bearings
▸Mining and construction equipment bearings
Benefits
- •Simpler sealing arrangement than oil systems (no pumps, filters, reservoirs)
- •Better protection against contamination ingress
- •Reduced lubricant consumption (no continuous leakage)
- •Lower initial system cost
- •Suitable for a wide temperature range with proper selection
Limitations
- •Limited heat dissipation compared to circulating oil
- •Grease degrades over time (oxidation, shear, oil separation)
- •Difficult to inspect without disassembly
- •Not suitable for very high speeds (oil mist or jet preferred)
Best Practices
- •Fill bearings slowly to avoid trapping air pockets
- •Distribute grease evenly around the bearing circumference
- •Run bearings for 10-30 minutes after initial greasing to distribute grease
- •Use the correct NLGI grade for the application
- •Never mix incompatible grease types (different thickeners)
Common Misconceptions
Myth: More grease is better for bearing protection.
Truth: Over-greasing is one of the most common causes of bearing failure. Excess grease causes churning, temperature rise of 10-20 C, accelerated grease degradation, and can damage seals. The correct fill is 25-45% of free space.
Myth: All greases are compatible with each other.
Truth: Mixing greases with different thickeners (lithium, calcium, polyurea) can cause incompatibility, resulting in softening or hardening of the mixture. Always purge old grease before switching types.
Myth: Grease lasts the life of the bearing.
Truth: Few bearings are permanently lubricated for life. Most require regreasing at regular intervals. Grease life depends on temperature, speed, contamination, and load conditions.
Practical Tips
- •For sealed bearings, the initial fill by the manufacturer is typically optimal - do not add more grease
- •Grease life halves for every 15 C increase above 70 C operating temperature
- •Use the NLGI consistency grade recommended by the bearing manufacturer (typically NLGI 2 for general use)
- •For electric motors, use grease with electrical conductivity (carbon black additive) to prevent bearing fluting
- •Purge old grease during regreasing until fresh grease appears at the seal - do not over-purge
- •Store grease in a clean, climate-controlled environment - contaminated grease is the #1 source of bearing contamination
- •The speed factor n x d_m (RPM x mm) determines the grease selection: < 200,000: NLGI 2, 200,000-400,000: NLGI 1-2, > 400,000: NLGI 0-1
Common Mistakes
Filling the bearing housing completely with grease
Never fill more than 1/3 to 1/2 of the housing free space. The remaining volume allows space for grease to be expelled and for heat dissipation.
Using the same grease for all applications
Match grease type to the specific application: base oil viscosity, thickener type, NLGI grade, and additives (EP, anti-wear, corrosion inhibitors) must be appropriate for the operating conditions.
Regreasing too frequently or infrequently
Use calculated intervals as a baseline and adjust based on operating conditions. Too frequent regreasing wastes grease and can damage seals; too infrequent risks lubrication starvation.
Ignoring grease degradation indicators
Monitor for: hardened grease at the seal, discoloration (darkening indicates oxidation), oil separation (bleeding), and metallic particles. These indicate it is time for a full regrease or bearing replacement.
Assumptions
This calculator makes the following assumptions to provide estimates:
Standard Bearing Geometry: The formula assumes standard bearing proportions. Non-standard or custom bearings may have different free volume fractions.
Grease Density 0.9 g/cm: The calculation assumes typical lithium complex grease density. Specialty greases (fluoroether, silica) have different densities.
Moderate Speed Operation: The 35% initial fill is optimized for moderate speed factors. High-speed bearings need reduced fill fractions.
Horizontal Shaft Orientation: The calculation assumes horizontal shaft mounting. Vertical shafts and other orientations require fill adjustments.
Limitations
Be aware of these limitations when using this calculator:
No Load or Vibration Effects: Grease life and distribution are affected by load magnitude and vibration, which are not modeled in this simple calculation.
Generic Interval Estimate: Relubrication intervals are estimated based on general experience. Actual intervals depend on specific operating conditions and grease quality.
Single Bearing Only: The calculation addresses individual bearings. Complex multi-bearing systems or bearing arrangements may require different approaches.
No Contamination Modeling: Contamination ingress (dust, moisture, process chemicals) can dramatically reduce grease life and is not accounted for in the interval calculation.
Frequently Asked Questions
Answers to common questions about this calculator.
What is the optimal grease fill for a bearing?
The optimal initial grease fill is 25-45% of the bearing free space, with 35% as the general recommendation. High-speed bearings need less (25%), slow-speed contaminated environments need more (45%). The free space is the volume inside the bearing not occupied by rolling elements and the cage.
How do I calculate grease quantity for a bearing?
Use the empirical formula Q = D x B x 0.005, where D is the bearing outer diameter in mm and B is the bearing width in mm. The result is the total grease quantity in grams for a full pack. Multiply by 0.35 for initial fill.
What happens if I over-grease a bearing?
Over-greasing increases churning losses, causing the bearing to run 10-20 C hotter. Higher temperature accelerates grease degradation (oil separation, oxidation), can damage seals, and may cause grease to leak into windings (motor failures) or product (contamination). Operating temperature typically stabilizes within 30-60 minutes of over-greasing.
What happens if I under-grease a bearing?
Under-greasing leads to lubricant starvation, metal-to-metal contact, increased friction and wear, and ultimately bearing failure by spalling or seizure. Noise, vibration, and temperature fluctuations signal starvation. Immediate regreasing is required if signs are detected.
How often should I regrease a bearing?
Regreasing intervals depend on bearing type, speed, temperature, and operating environment. General guidelines: 1500-4000 hours for ball bearings, 1000-3000 hours for roller bearings. Adjust for temperature (halve interval for every 15 C above 70 C) and speed (inverse proportional to speed factor).
What is the speed factor n x d_m?
The speed factor is the product of rotational speed n (RPM) and the mean bearing diameter d_m (mm), where d_m = (D + d)/2. It characterizes the speed severity of a bearing application and is used to select grease type and determine relubrication intervals.
What NLGI grade should I use?
NLGI 2 is the most common grade for general bearing applications. Use NLGI 1 or 0 for high-speed applications (n x d_m > 300,000) or centralized lubrication systems. Use NLGI 3 for very slow-speed, heavy-load bearings where leakage would be problematic.
How does temperature affect grease life?
Grease life follows an Arrhenius relationship. For every 15 C increase above 70 C, the grease life approximately halves. At 100 C, grease life is about 1/4 of that at 70 C. High-temperature greases (synthetic oils, PTFE thickeners) are required for continuous operation above 120 C.
What is the difference between NLGI grades?
NLGI (National Lubricating Grease Institute) grades indicate grease consistency measured by worked penetration: 000 (very fluid, 445-475), 00 (semi-fluid, 400-430), 0 (very soft, 355-385), 1 (soft, 310-340), 2 (medium, 265-295), 3 (firm, 220-250), 4-6 (increasingly hard). Most bearings use NLGI 2.
Can I mix different grease types?
Mixing greases with incompatible thickeners can cause the mixture to soften (leak out) or harden (block grease paths). The most common incompatibility is lithium vs. polyurea thickeners. Always consult the grease compatibility chart and purge the old grease completely before switching types.
What is grease bleeding and is it normal?
Grease bleeding (oil separation) is a normal phenomenon where the base oil separates from the thickener. A small amount of bleeding is essential for bearing lubrication as the free oil supplies the rolling contacts. Excessive bleeding indicates grease degradation or improper formulation.
How do I select the right base oil viscosity in grease?
The base oil viscosity in grease should match what would be used for oil lubrication of the same bearing. For most industrial bearings, ISO VG 100-320 is typical. Higher viscosity for slower speeds, heavier loads, or higher temperatures. Use the n x d_m speed factor and bearing manufacturer recommendations.
What is the effect of water contamination on grease?
Water contamination (even 1000 ppm) accelerates grease degradation, causes corrosion of bearing surfaces, and can wash out grease from critical contact areas. Water reduces grease consistency, promotes oil separation, and can lead to early bearing failure. Use water-resistant greases (calcium sulfonate, aluminum complex) in wet environments.
How do I grease a sealed bearing?
Sealed bearings (2RS, 2Z shields) are pre-greased at the factory and cannot be regreased in service. Do not attempt to add grease through seals or shields. When the grease degrades or the bearing fails, replace the entire bearing. Shielded bearings have slightly longer grease life than sealed due to lower friction.
What is the proper procedure for greasing a bearing?
1) Clean the grease fitting. 2) Remove the drain plug (if present). 3) Add grease slowly while the bearing is rotating (if possible). 4) Stop when fresh grease appears at the drain or seal. 5) Run for 10-30 minutes to stabilize. 6) Check temperature and re-tighten fittings. Over-greasing is more harmful than under-greasing.
How does vibration affect grease performance?
Vibration accelerates grease mechanical degradation through shear and can cause grease to migrate away from rolling elements. It also promotes oil separation (syneresis). For high-vibration applications, use greases with high mechanical stability (tested by ASTM D217 worked stability) and higher viscosity base oils.
What is the shelf life of grease?
Most greases have a shelf life of 2-5 years when stored in sealed containers at 10-30 C. Over time, grease can separate (oil on top, thickener settled), oxidize, or absorb moisture. Always inspect grease before use and check for discoloration, oil separation, or contamination.
How do I determine if grease needs to be replaced?
Indicators: darkening (oxidation), oil separation (bleeding), hardening (shear degradation or oxidation), metallic particles (wear), water contamination (cloudy appearance, rust). Oil analysis (FTIR, viscosity, particle count) provides quantitative assessment. Replace if the bearing is running hot, noisy, or due for scheduled maintenance.
What is the role of additives in grease?
Additives enhance grease performance: anti-oxidants extend life, EP (extreme pressure) additives protect under heavy loads, anti-wear additives (ZDDP) reduce surface damage, rust inhibitors prevent corrosion, tackiness agents improve adhesion, and solid lubricants (MoS2, graphite) provide backup lubrication under boundary conditions.
How does bearing speed affect grease requirements?
Higher speeds generate more frictional heat and shear the grease more severely, requiring smaller grease fills (25-30% vs 35-45%) and softer NLGI grades (1 or 0 vs 2). Very high speed bearings (spindle, turbine) often use oil lubrication instead of grease due to heat dissipation limitations.
What is the correct drain plug practice for greasing?
Always remove the drain plug (bottom or side) before greasing. This allows old grease and excess new grease to escape, prevents pressure buildup that could blow seals, and provides visual confirmation that fresh grease has reached the bearing. Replace the drain plug after 10-30 minutes of operation.
How do I calculate grease quantity for multiple bearing housings?
Calculate each bearing individually, then sum the quantities. For housings containing two bearings (e.g., pillow block), fill the space between bearings 30% full. The total housing fill should not exceed 50% of the free space in the housing.
What is the difference between grease and anti-seize compound?
Grease is a lubricant designed to reduce friction and wear between moving surfaces. Anti-seize compound is a high-temperature assembly paste containing metal powders (copper, aluminum, nickel) that prevents galling and seizure of threaded fasteners and press-fitted parts. Never use anti-seize as a bearing lubricant.
How do I select grease for high-temperature applications?
For temperatures above 120 C: use synthetic base oils (PAO, ester, silicone, PFPE) with high-temperature thickeners (PTFE, polyurea, fluorinated). Standard lithium greases degrade rapidly above 120 C. PFPE (perfluoropolyether) greases can operate to 250 C but are very expensive.
What is the effect of dust and particulate contamination on grease?
Dust contamination acts as an abrasive, increasing wear of rolling surfaces and reducing bearing life by 50-90%. Particles also catalyze grease oxidation. Use sealed bearings or effective labyrinth seals with purgeable grease systems in dirty environments. Regrease more frequently to flush out contaminants.
How does grease lubrication differ from oil lubrication?
Grease provides all-day lubrication without the need for oil supply systems (pumps, filters, reservoirs). However, grease has limited heat dissipation ability, cannot be filtered for contaminant removal, and requires periodic replacement. Oil systems can achieve lower friction, higher speeds, and better cooling.
What is the significance of grease channeling?
Grease channeling is the desirable behavior where grease forms a barrier around the rolling elements without being continuously worked. Proper channeling reduces churning and temperature rise while maintaining a reservoir of oil near the contacts. NLGI 2 greases typically channel well at moderate speeds.
How do I determine the right regreasing interval for critical bearings?
Use bearing manufacturer software (SKF, FAG, NSK) or empirical formulas as a starting point. Then: 1) Monitor bearing temperature trends. 2) Analyze used grease samples at intervals. 3) Use vibration analysis (grease starvation shows specific vibration signatures). 4) Adjust interval to maintain optimal conditions. Most critical bearings benefit from condition-based relubrication.
What are the safety considerations for grease disposal?
Used grease may contain heavy metals (from wear particles and additives) and should be disposed of as hazardous waste in most jurisdictions. Never mix used grease with general waste or pour down drains. Collect in sealed containers and arrange for licensed waste oil/grease recycling.
Can grease be regenerated or recycled?
Grease cannot be readily recycled due to its complex structure. Some facilities separate the oil from the thickener for waste-to-energy conversion. The best environmental practice is to minimize consumption through proper fill quantities and extended intervals, and to use biodegradable greases (vegetable oil based) where appropriate.
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Glossary
Technical terms used in mortgage calculations explained in plain language.
- Bleeding
- Separation of base oil from the grease thickener. Controlled bleeding is necessary for lubrication; excessive bleeding indicates instability.
- Channeling
- Desired grease behavior where the grease forms a channel around rolling elements without being continuously worked, reducing churning.
- Churning
- Excessive mechanical working of grease causing temperature rise, shear degradation, and accelerated oil separation.
- NLGI Grade
- National Lubricating Grease Institute consistency classification from 000 (fluid) to 6 (solid). NLGI 2 is the most common bearing grease.
- n x d_m Factor
- Speed factor = rotational speed (RPM) x mean bearing diameter (mm). Used for grease selection and relubrication interval calculation.
- Over-greasing
- Filling a bearing with more grease than the free space can accommodate, causing churning, overheating, and seal damage.
- Relubrication Interval
- Recommended time between grease additions. Determined by bearing type, speed, temperature, and operating environment.
- Shear Degradation
- Permanent loss of grease consistency due to mechanical working. Measured by the ASTM D217 rolled stability test.
- Speed Factor
- Product of bearing rotational speed and mean diameter (n x d_m). Key parameter for grease selection and life estimation.
- Thickener
- Solid component of grease (typically lithium soap, polyurea, calcium sulfonate) that forms the structure holding the base oil.
Authoritative References
Trusted sources and standards referenced by this calculator.
SKF Grease Selection and Quantity Guide FAG Rolling Bearing Lubrication Manual ASTM D217 - Grease Cone Penetration Test NLGI Lubricating Grease Guide ISO 2137 - Grease Penetration Standard STLE - Grease Lubrication Fundamentals
Applicable Standards
ASTM D217ISO 2137DIN 51825AGMA 9005ISO 6743-9NLGI RB
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Last Updated:
2026-07-30
Version:
2.0.0
References:
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Free to use for educational and professional purposes.