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Capsule Volume & Packstat Calculator

Convert between capsule sizes and volumes, estimate packstats from powder density, and convert known packstats across capsule sizes. Essential for compounding pharmacy capsule formulation.

Disclaimer: This tool is provided for informational and educational purposes only. Results should always be independently verified by a qualified healthcare professional before use in clinical practice. Compound Direct accepts no liability for errors or clinical decisions made based on these calculations.

Density Warning

Calculated packstats are theoretical estimates based on the density value provided. Tap density differs from tamped (compressed) density, which differs from bulk density. Always verify calculated values against real-world capsule packing tests before use in production.

Section A: Capsule Volume Reference

Compare capsule sizes, volumes, and typical capacities

Capsule Size Chart (to scale)

Click a capsule to view details. Dimensions shown as diameter x length.

0mm5mm10mm15mm20mm25mm0009.91mm26.1mm008.53mm23.3mm07.65mm21.7mm16.91mm19.4mm26.35mm18mm35.82mm15.9mm45.31mm14.3mm54.91mm11.1mm

Size

0

Volume

0.68

mL

Diameter

7.65

mm

Length

21.7

mm

Typical Capacity

500

mg (avg density)

SizeDiameter (mm)Length (mm)Volume (mL)Typical Capacity (mg)Relative to Size 0
0009.9126.11.371000201%
008.5323.30.91735134%
07.6521.70.68500100%
16.9119.40.540074%
26.35180.3730054%
35.8215.90.324044%
45.3114.30.2118031%
54.9111.10.1312019%

Section B: Density to Packstat

Given a powder density and dose, see the fill level for each capsule size

Section C: Packstat Size Converter

Convert a known packstat from one capsule size to estimate packstats for other sizes

Only sizes 000, 00, 0, and 1 are available as source — smaller sizes have too much margin of error for reliable conversion.

How to Use This Tool

Section A: Capsule Volume Reference
  1. Click a capsule on the chart to view its volume and typical capacity
  2. Use the visual comparison to understand relative sizing and dimensions
Section B: Density to Packstat
  1. Enter the powder density in g/mL or mg/mL
  2. Enter the required dose in mg
  3. View the fill percentage and feasibility for each capsule size
Section C: Packstat Converter
  1. Select the capsule size you have a known packstat for (size 1 or larger)
  2. Enter the known packstat (mg)
  3. View the estimated packstat for all other capsule sizes

Formula & Methodology

Volume-Based Calculations

Capsule packstat estimation is based on the relationship between powder bulk density, capsule volume, and the required dose.

Powder Volume Required:

Volume (mL) = Dose (g) / Density (g/mL)

Fill Percentage:

Fill % = Volume Required / Capsule Volume x 100

Packstat Conversion:

Packstat_B = Packstat_A x (Volume_B / Volume_A)

Density Considerations

Powder density varies significantly depending on how the measurement is taken:

  • Bulk density: Loosely poured powder — lowest density
  • Tap density: Powder settled by tapping — higher than bulk
  • Tamped density: Manually compressed into capsule — highest density, most representative of actual packing

The density used in these calculations should ideally match the packing method used in your compounding workflow.

Packstat Size Conversion Limitations

Converting a packstat from one capsule size to another assumes uniform density. This assumption holds better when the source capsule is large enough (size 1 or bigger) to minimise measurement error. Smaller capsules have proportionally larger margins of error due to their reduced volume, making inferred conversions unreliable.

Frequently Asked Questions

What is a capsule packstat?
A packstat (or pack stat) is the maximum amount of a specific powder that can be packed into a given capsule size, typically expressed in milligrams. It depends on the powder's density and the packing method used.
Why can I only convert packstats from size 1 or larger?
Smaller capsules (sizes 2-5) have very low volumes. Small measurement errors in the known packstat become proportionally large when scaled up, making the converted values unreliable. Size 1 and above provide enough volume for a reliable density inference.
Should I use tap density or tamped density?
Use the density that most closely matches your actual packing method. Tap density is measured by mechanical tapping and is a standardised measurement. Tamped density (manually pressing powder into the capsule) more closely represents actual compounding conditions but is less reproducible. Always verify calculated packstats against real-world packing tests.
How accurate are the packstat conversions?
Packstat conversions assume uniform powder density across capsule sizes. In practice, packing efficiency can vary with capsule geometry. Treat converted values as estimates and always validate with physical packing tests, especially for new formulations.

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