Monday, July 6, 2026
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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 maximum fill weight for a target capsule size. Essential for early-stage oral solid formulation development and tech transfer.

Quick Answer

Capsule size is selected from fill volume: fill volume (mL) = fill weight (mg) ÷ bulk density (g/mL) ÷ 1000. Compare to standard hard gelatin capsule volumes — size 0 holds ~0.68 mL, size 00 ~0.91 mL. Aim for 70–95% fill utilisation for reliable cap closure. Bulk density typically ranges 0.2–1.0 g/mL; use 0.5 g/mL as a development default until measured. Verify in pilot filling trials with actual powder flow.

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

Enter API dose, blend percentage or total fill weight, and bulk density to find the recommended capsule size.

API and fill weight
Leave blank to enter fill weight directly
Powder properties
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.

Pharma & formulation development context

Capsule size selection is one of the earliest formulation decisions and affects API loading, patient acceptability, and manufacturing feasibility. Development teams measure loose and tapped bulk density during preformulation, then confirm selected size in exhibit and pilot batches on target filling equipment before locking the master formula.

This calculator integrates with the NovaPharmaNews manufacturing hub: track batch yield with the Pharmaceutical Yield Calculator, assess blend properties, plan dilutions with the Dilution Calculator, and convert concentrations with the Molarity Calculator.

Bulk density: Measure for your actual powder blend — values directly determine fill volume. HGC vs HPMC: Hard gelatin is most common; HPMC is preferred for hygroscopic APIs. Maximum size: Size 00 is generally the largest accepted for adult patients; 000 is mainly veterinary or pellet systems.

Evidence & sources

Frequently Asked Questions

Capsule size is selected based on fill volume required to accommodate the formulation at target fill weight. Fill volume = fill weight (mg) ÷ bulk density (g/mL) ÷ 1000. The calculated volume is compared to rated capsule volumes; the smallest size holding 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 powder, granules, pellets, or other formulation that physically occupies the capsule body. Calculated as fill weight (g) ÷ bulk density (g/mL). The fill should not exceed 80–90% of capsule body volume to allow cap closure. Rated volumes include both body and cap when joined.
Bulk density is the mass of powder per unit volume in its uncompacted (loose) state, typically g/mL. It varies from 0.2 g/mL for fluffy materials to over 1.0 g/mL for dense granules. Default 0.5 g/mL is common when no measured value exists. Tapped density is typically 10–40% higher and more relevant for tamping capsule fillers.
Fill should occupy approximately 70–90% of total capsule volume for reliable cap closure. On high-speed filling lines, nominal overfill of 5–10% by weight accounts for weight variation. Exact acceptable range is defined in the product fill weight specification in the batch manufacturing record.
Size 0 has nominal fill volume ~0.68 mL; size 00 holds ~0.91 mL — about 34% larger. Smaller numbers indicate larger capsules (000 largest, 5 smallest). Size 00 is common for high-dose products; size 0 is the most widely used adult oral solid size. Both available in HGC and HPMC grades.
Loose bulk density is measured by gently pouring powder into a container without compaction — relevant for gravity-fed or dosator filling. Tapped bulk density is measured after standardised tapping/vibration — higher and more representative of compacted powder in tamping pin fillers. Using the wrong density type causes incorrect capsule size selection.
Switch when fill utilisation exceeds ~95% at size 0 — high utilisation risks cap closure failure and weight variation. Alternatively, increase excipient level to reduce fill weight per capsule while maintaining API dose. For doses exceeding size 000 volume (~1.37 mL), consider split dosing, alternative dosage forms, or pellet/MUPS systems.
HPMC capsules have nominally identical rated volumes to hard gelatin capsules, but manufacturer datasheets may list slightly different values. HPMC is preferred for hygroscopic APIs and moisture-sensitive drugs because it is less moisture-sensitive than gelatin. Always confirm volumes with the specific capsule supplier.
Total fill weight = API dose ÷ (API % ÷ 100). A 200 mg API at 50% in blend requires 400 mg total fill weight including excipients. Higher API loading reduces fill weight and may allow a smaller capsule size. Low API loading increases excipient mass and fill volume.
Target 70–95% fill utilisation. Below 50% suggests an oversized capsule causing rattling and weight variation. Above 95% risks cap closure problems and cracking under tamping pressure. High-speed rotary capsule fillers may require slightly lower utilisation than manual filling depending on powder flow and tamping settings.
Max fill weight (mg) = capsule volume (mL) × fill level (%) ÷ 100 × bulk density (g/mL) × 1000. Mode B in this calculator performs this reverse calculation. Example: size 0 (0.68 mL) at 90% fill and 0.5 g/mL density = 0.68 × 0.9 × 0.5 × 1000 = 306 mg.
No. Calculated capsule size is a development starting point. Actual fill weight varies with dosing disc depth, tamping force, powder flow (Carr Index, Hausner Ratio), humidity, and equipment type. Pilot batches on target filling equipment are required before locking capsule size in the master formula and registration dossier.

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