00 Capsule Size: Gelatin and Empty Capsule Size Chart, Capacity, and Milligram Guide

The 00 capsule size is one of the most widely used formats in dietary supplement manufacturing and home compounding. Understanding its volumetric capacity helps formulators, pharmacists, and consumers ensure accurate dosing. The gelatin capsule size chart and its vegetarian equivalent provide a standardized reference for selecting the right shell for a given powder weight, density, and dose requirement. If you’ve wondered how much does a 00 capsule hold, the answer depends on the material’s bulk density—but clear numbers and comparisons exist to guide the choice.

Referencing an empty capsule size chart before filling is essential because different powders pack differently. A 00 capsule size holds roughly 735 milligrams of an average-density powder, though this figure ranges from approximately 400 mg for light, fluffy materials to over 1,000 mg for dense compounds. Knowing how many mg in 00 capsule applications can realistically fit prevents under- or overfilling and maintains product integrity.

Understanding the Capsule Size Numbering System

How Capsule Sizes Are Numbered

Capsule size numbering runs counterintuitively: smaller numbers indicate larger capsules. The standard range spans from size 5 (the smallest, holding roughly 130 mg of average powder) to size 000 (the largest commonly used, holding up to 1,600 mg). The 00 capsule size sits second-largest in this scale, between size 0 and size 000.

A complete gelatin capsule size chart typically includes length in millimeters, external diameter, locked and open fill lengths, and volumetric capacity in milliliters. For the 00 size, total locked length is approximately 23.3 mm, external diameter roughly 8.5 mm, and volume approximately 0.91 mL. Vegetarian HPMC capsules in the same size carry nearly identical volumetric specifications, making the empty capsule size chart applicable across shell material types.

Comparing Adjacent Sizes

Choosing between a 0 capsule and a 00 capsule is common when a formulation falls near the upper edge of the smaller size. A size 0 holds approximately 680 mg of average powder, while the double-zero shell holds about 735–750 mg. If the required dose exceeds 680 mg but patient swallowability is a concern, splitting the dose across two size 0 capsules may be preferable to one large 00 shell.

Filling and Capacity Calculations

Bulk Density and Its Impact on Capacity

The most important variable in any capsule filling calculation is bulk density, measured in grams per milliliter. A low-density herbal powder might pack at 0.3 g/mL, meaning a 0.91 mL capsule holds only about 273 mg—far less than the average-density estimate. Conversely, a dense mineral salt at 1.1 g/mL fills the same gelatin capsule to over 1,000 mg.

Formulators calculate target fill weight by multiplying the capsule’s volume in milliliters by the bulk density of the specific powder blend. This number guides machine settings for automated capsule fillers and helps verify that hand-filling produces consistent results. For compounding pharmacies, this calculation is documented in master formulation records as part of standard quality assurance.

Practical Filling Techniques

Manual capsule-filling trays align multiple shells simultaneously, allowing tamping tools to compress loose powder and maximize fill. Tamping increases fill weight by 20 to 30 percent compared with loose pouring alone, which can make the difference between fitting a dose into one or two shells. For home use, a handheld tamp and filling board for 00 capsule size handling are widely available and straightforward to use.

Material Types and Special Considerations

Standard gelatin capsules are bovine- or porcine-derived and dissolve within 5 to 10 minutes in stomach acid. Vegetarian HPMC shells dissolve more slowly and may be preferred for acid-sensitive compounds or for vegetarian and vegan consumers. Enteric-coated capsules pass through the stomach intact and release in the small intestine—relevant for probiotic or enzyme formulations that degrade in acidic environments.

Moisture and humidity management matters when storing empty capsule size chart quantities in bulk. Gelatin shells become brittle below 10 percent relative humidity and sticky above 60 percent. Ideal storage is 35 to 55 percent relative humidity at room temperature, in sealed bags away from direct light. HPMC capsules tolerate a slightly broader humidity range.

Key takeaways: The 00 capsule size holds approximately 735 mg of average-density powder, though actual capacity varies significantly with bulk density. Always reference a current gelatin capsule size chart or empty capsule size chart before finalizing a formulation, and verify milligram estimates using a bulk density measurement of your specific powder.