NLGI Grease Grade to Consistency Converter

The NLGI (National Lubricating Grease Institute) grading system classifies greases by their consistency (firmness) on a scale from 000 (most fluid) to 6 (hardest block). The grade is determined by the worked penetration test defined in ASTM D217, which measures how far a standard cone sinks into the grease under a specified weight and time.

How the NLGI test works: A standard cone weighing 102.5 grams (with shaft assembly totaling 150 grams) is allowed to sink into a grease sample at 25C (77F) for exactly 5 seconds. The depth of penetration is measured in tenths of a millimeter. This measurement is called the “worked penetration” because the grease sample is first mechanically worked (stirred) 60 double strokes in a standard grease worker to simulate actual service conditions.

NLGI grade table:

NLGI Grade 2 is by far the most commonly used. It accounts for roughly 50% of all grease sold worldwide. Grade 2 stays in place in most bearings and joints, works across a wide temperature range, and can be applied with standard grease guns.

The food comparisons the calculator prints (cooking oil, applesauce, mustard, tomato paste, peanut butter, shortening, frozen yogurt, pate, cheddar) are the NLGI’s own published analogy chart, not something invented here. Frozen yogurt for Grade 4 catches people out because it sounds softer than the shortening at Grade 3, but the chart means a firm, fully frozen block rather than the soft-serve version.

Applications by grade:

Grades 000 and 00 (fluid greases): Used in enclosed gearboxes, centralized lubrication systems, and applications where the grease must flow through long supply lines. They behave almost like thick oils and are sometimes called “semifluid greases.”

Grade 0 and 1 (soft greases): Used in centralized systems with shorter lines, slow-speed bearings, and cold-weather applications. The softer consistency allows easier pumping at low temperatures.

Grade 2 (normal): The standard multipurpose grade. Used in wheel bearings, ball joints, chassis points, electric motors, industrial bearings, and most general lubrication. If a manual does not specify a grade, Grade 2 is usually the correct choice.

Grade 3 (firm): Used in applications where grease must resist being thrown out by centrifugal force, such as vertical shafts, high-speed bearings, and applications with loose fits. Also used in water-exposed environments where a firmer grease stays in place better.

Grades 4-6 (very firm to block): Specialized applications such as slow-moving open gears, dam gates, and brick-form lubricants. These grades are applied by hand or with special applicators rather than standard grease guns.

Temperature effects on consistency: Grease softens when heated and stiffens when cooled. A Grade 2 grease at -20C may behave like a Grade 3 or 4, while the same grease at 80C may soften to Grade 1 consistency. The dropping point (temperature where grease turns fully liquid) ranges from roughly 95-145C for calcium greases (depending on type) to over 260C for polyurea greases.

Mind the gaps between the bands. The ranges are 30 units wide with 15 units of dead space between them, so a lab result of 390 belongs to no grade at all. It sits between Grade 0 (355-385) and Grade 00 (400-430). That is not a mistake in the standard, it is deliberate: the gaps stop borderline batches from being labelled either way. A tested value landing in a gap means the grease is genuinely off-grade, usually because it has been over-worked, contaminated, or has started to bleed its base oil.

Reading a penetration number backwards. Datasheets and lab reports quote worked penetration rather than a grade, and the two are easy to mix up because the scale runs backwards: a higher penetration number means a softer grease. The cone sinks further into the soft one. Enter a penetration value below and the page names the grade it falls in, or tells you which two grades it fell between.