Capsule filling · Industry glossary
Hausner ratio (HR)
The ratio of a powder’s tapped density to its loose bulk density.
Also called: Hausner number.
Hausner ratio formula and units
Divide tapped density by loose bulk density using consistent units and defined measurements of the same powder. The units cancel. A result such as 1.33 is a ratio, not 1.33% and not a mass or flow rate.
For an unchanged sample mass, density equals mass divided by volume. The same ratio can therefore be written as initial bulk volume divided by final tapped volume. This equivalence assumes the mass is the same; it does not specify a tapping procedure.
HR = tapped density / bulk density = bulk volume / tapped volume (same mass)
What does a higher Hausner ratio mean?
It means a larger tapped-to-loose density difference in the measurements being compared. That is a statement about packing change; it is not a direct measurement of how fast powder passes through a hopper.
A result depends on the loose preparation and the tapping method, so retain both density values and the sample condition. An unexpected ratio below one calls for clarification of those inputs and conditions rather than assigning a flow grade from the number alone.
Is Hausner ratio an independent check on Carr index?
No. Calculated from the same two density measurements, Hausner ratio and Carr index are alternative expressions of the same packing change. Reporting both adds a second format, rather than an independent experiment.
Density indices can be useful descriptors, but their empirical labels do not by themselves demonstrate capsule-filling performance. Material-specific behaviour under the intended process remains a separate question.
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