Enter powder test inputs
Use one column on phones, two on medium screens, and three on large screens. Densities here are based on g/mL, which matches g/cm³ numerically.
Example data table
These sample records help verify calculator behavior and provide quick benchmarks for common powders.
| Material | Bulk Density (g/mL) | Tapped Density (g/mL) | Hausner Ratio | Carr Index (%) | Angle of Repose (°) | Typical Flow Class |
|---|---|---|---|---|---|---|
| Granulated sugar | 0.82 | 0.88 | 1.073 | 6.82 | 29.5 | Free flowing |
| Spray dried milk powder | 0.47 | 0.56 | 1.191 | 16.07 | 36.0 | Moderate flow |
| Microcrystalline cellulose | 0.31 | 0.40 | 1.290 | 22.50 | 42.5 | Cohesive |
| Talc | 0.28 | 0.39 | 1.393 | 28.21 | 49.0 | Very cohesive |
Formula used
Bulk Density = Sample Mass ÷ Bulk Volume
Tapped Density = Sample Mass ÷ Tapped Volume
Hausner Ratio = Tapped Density ÷ Bulk Density
Carr Index (%) = ((Tapped Density − Bulk Density) ÷ Tapped Density) × 100
Angle of Repose = arctan(Cone Height ÷ Cone Radius)
Mass Flow Rate = Discharge Mass ÷ Discharge Time
Orifice Area = π × (Orifice Diameter ÷ 2)²
Specific Discharge = Mass Flow Rate ÷ Orifice Area
Porosity (%) = (1 − Bulk Density ÷ True Density) × 100
Powder Flow Index = 0.35 × Angle Score + 0.30 × Hausner Score + 0.25 × Carr Score + 0.10 × Rate Score
How to use this calculator
- Enter the measured sample mass used in your flowability test.
- Provide loose bulk volume and tapped volume from a graduated cylinder or similar method.
- Measure the powder cone height and base diameter after free pouring.
- Enter the mass discharged and the time needed through the selected outlet.
- Add orifice diameter, moisture content, true density, and particle size if available.
- Press the calculate button to display results above the form.
- Review the chart, result table, and flow class for quick interpretation.
- Use the CSV or PDF buttons to save the current result set.
FAQs
1) What does the powder flow index represent?
It is a composite screening score built from angle of repose, Hausner ratio, Carr index, and discharge behavior. It helps compare powders quickly during formulation, storage, and transfer studies.
2) Why are both bulk and tapped volumes needed?
They reveal how much the powder consolidates under vibration or tapping. That consolidation behavior strongly affects hopper discharge, feeder consistency, and the likelihood of arching or rat-holing.
3) Is a lower angle of repose always better?
Usually yes for free-flowing bulk solids. A lower angle suggests reduced friction and cohesion, though the best operating target still depends on particle shape, moisture, and equipment geometry.
4) What Hausner ratio indicates poor flow?
Values above about 1.25 often indicate poorer flow and greater consolidation sensitivity. Higher values generally mean the powder packs significantly when disturbed or vibrated.
5) How should I interpret the Carr index?
Lower values usually mean better flow. A Carr index below 15 is often considered good, while values above 25 can indicate more cohesive and compressible powder behavior.
6) Does moisture affect powder flow a lot?
Yes. Even modest moisture increases can raise interparticle adhesion, worsen caking, and reduce repeatable discharge. Hygroscopic materials are especially sensitive during storage and conveying.
7) Can this calculator replace shear cell testing?
No. It is useful for fast screening and comparison, but critical hopper or silo design should still use validated shear testing and material-specific engineering data.
8) Which industries use powder flow assessments?
Common users include pharmaceutical, food, additive manufacturing, ceramics, chemicals, minerals, battery materials, and powder metallurgy teams that handle dosing, blending, and discharge operations.