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Pharmaceutical Calculators

Capsule Fill Weight Calculator

Determine the correct hard gelatin capsule size from fill weight and bulk density, or calculate the maximum fill weight for a target capsule size. Essential for early-stage oral solid formulation development.

Capsule Size Reference Table
Size Fill Volume (mL) Typical Fill Wt at 0.5 g/mL (mg) Notes
0001.37685Largest; rarely used, mostly veterinary
000.91455High-dose products
00.68340Most common adult size
10.50250Common adult size
20.37185Medium dose
30.30150Low-dose / paediatric
40.21105Paediatric
50.1365Smallest; paediatric / micro-dose

Fill volumes are for standard hard gelatin capsules (HGC). HPMC (vegetarian) capsules have nominally identical rated volumes but may differ slightly by manufacturer. Volumes shown are the complete joined capsule.

Mode A — Determine Capsule Size from Fill Weight
Leave blank to enter fill weight directly
Fill Volume
—
mL
Recommended Size
—
Capsule Volume
—
mL
Fill Utilisation
—
%

How to Use

1
Mode A: Enter the API dose and either the % API in the blend (to auto-calculate total fill weight) or enter total fill weight directly. Input bulk density (default 0.5 g/mL) and click Calculate.
2
The recommended capsule size is highlighted in the reference table above. Fill utilisation % shows how much of the capsule volume is used — aim for 80–95% for reliable filling.
3
Mode B: Select a target capsule size, enter fill density and desired fill level %, to calculate the maximum fill weight achievable.
4
Verify selected size in pilot filling trials — actual fill weight varies with dosing disc depth, tamping force, and real-world powder behaviour.

Worked Example

Example Calculation — Finding Capsule Size

API dose = 200 mg  |  API in blend = 50%  |  Bulk density = 0.6 g/mL

Total fill weight = 200 mg ÷ 50% = 400 mg

Fill volume = 400 mg ÷ 0.6 g/mL ÷ 1000 = 0.667 mL

Capsule size 0 (0.68 mL) is the smallest size that can accommodate 0.667 mL.

Fill utilisation = 0.667 / 0.68 = 98% — slightly high; consider increasing excipient ratio or switching to size 00.

Formulation Considerations

Capsule size selection is one of the earliest formulation decisions and affects API loading, patient acceptability, and manufacturing feasibility. Key considerations include:

Bulk density: Measure loose and tapped bulk density for your actual powder blend — these values directly determine fill volume and influence selection between adjacent capsule sizes.

Hard gelatin vs HPMC capsules: Hard gelatin (HGC) capsules are the most common and have well-established fill volumes. Hydroxypropyl methylcellulose (HPMC) capsules are the vegetarian/vegan alternative. Their nominal volumes are essentially the same as HGC, but HPMC capsules are less moisture-sensitive and preferred for hygroscopic API formulations or moisture-sensitive drugs. Some specialty HPMC capsule manufacturers list slightly different volumes — always confirm with the specific capsule supplier's datasheet.

Maximum capsule size: For adult patients, size 00 is generally the largest accepted capsule; size 000 and above are mainly used in veterinary applications or for multiple-unit pellet systems (MUPS).

Frequently Asked Questions

Capsule size is selected based on the fill volume required to accommodate the formulation. Fill volume = fill weight (mg) ÷ bulk density (g/mL) ÷ 1000. The calculated volume is compared to rated capsule volumes; the smallest capsule that can hold the fill at 70–95% utilisation is selected. Size 0 (0.68 mL) and 00 (0.91 mL) are most common for adult oral solid dosage forms.
Fill volume is the volume of formulation material (powder, granules, pellets, mini-tablets) that physically occupies the capsule body. Calculated as fill weight (g) ÷ bulk density (g/mL). The fill should not exceed 80–90% of the capsule body volume to allow the cap to close properly. Rated capsule volumes include both body and cap when joined; usable body volume is somewhat less.
Bulk density is the mass of powder per unit volume in its loose, uncompacted state (g/mL). It ranges from about 0.2 g/mL for very fluffy materials to over 1.0 g/mL for dense granules. A default of 0.5 g/mL is used when no measured value is available. Tapped density (measured after standardised tapping) is typically higher and may be more representative of the compacted powder in a filled capsule.
The fill should occupy approximately 70–90% of the total capsule volume (body + cap) to allow reliable cap closure. On high-speed filling lines, a nominal overfill of 5–10% by weight is common to account for weight variation and to meet fill weight specifications across the batch. The exact acceptable range is defined in the product's fill weight specification in the batch manufacturing record.
Size 0 has a fill volume of approximately 0.68 mL; size 00 holds approximately 0.91 mL — about 34% larger. The numbering system is counterintuitive: smaller numbers indicate larger capsules (000 is the largest, 5 the smallest). Size 00 is used for higher-dose products, while size 0 is the most common adult oral solid dosage form. Both are available in hard gelatin (HGC) and HPMC vegetarian grades.

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