One of the most common questions we hear from herbalists and home formulators is simple: what capsule size should I use? It's an easy thing to overlook until you're standing in front of your capsule machine wondering why the capsules you bought don't fit. This guide walks through how capsule sizing works, how it affects fill volume, and how to match the right size to your machine and your ingredients.
JUMP TO: Understanding Capsule Sizes, How Capsule Size Affects Fill Volume Matching, Capsule Size to Your Machine, Gelatin vs. Vegetarian Capsules, Choosing a Size for Your Use Case FAQ
Understanding Capsule Sizes
Capsule sizes run on a numbered scale, with smaller numbers meaning a larger capsule. Capsule sizes run on a numbered scale, with smaller numbers meaning a larger capsule. The most common sizes, from largest to smallest, are 000, 00, 0, 1, 2, 3, 4, and 5. For home and small-batch herbal use, size "0" and size "00" are popular options because they offer useful fill volumes.
Size "00" is the larger of the two, while size "0" is a bit smaller and may be easier for some people to swallow. Neither size is inherently better; the choice depends on the amount of powder, its density, and individual preference.
How Capsule Size Affects Fill Volume
The larger the capsule, the more powder it holds. Actual powder weight depends on bulk density and packing. At an illustrative bulk density of 0.8 g/mL, those volumes correspond to approximately 760 mg and 540 mg, respectively. Exact capsule volumes vary by manufacturer. Keep in mind that actual fill weight varies depending on the density of the powder you're using, since a fine, dense powder will pack differently than a light, fluffy one.
If your formulation requires more powder per capsule, size "00" may reduce the number of capsules needed per serving. If it requires less powder, or you prefer a smaller capsule, size "0" may be a better fit.
Matching Capsule Size to Your Machine
Capsule machines are designed for specific capsule sizes. Using the wrong size may prevent the base and cover from properly holding and closing the capsules.
At Monterey Bay Herb Co., we carry a capsule machine for size "0" and one for size "00". Both fill 24 capsules per batch and are designed for manual, small-batch use. Check the machine size before ordering capsules.
For a comparison of equipment types, see our manual vs. automatic capsule machines guide.
Gelatin vs. Vegetarian Capsules
Once you've settled on a size, you'll also need to choose between gelatin and vegetarian capsules. Gelatin capsules are made from animal-derived gelatin and have a long history of use in supplement making. Vegetarian capsules are commonly made from hydroxypropyl methylcellulose (HPMC), a cellulose-derived material, and are a common option for plant-based formulations. Confirm the composition of the specific capsule product before publishing.
Both options are available in sizes "0" and "00" in our herbal supplies range:
Both gelatin and vegetarian capsules can generally be used with compatible manual machines when the size matches. Check the machine manufacturer’s recommendations for capsule material and compatibility. The material choice also depends on formulation and customer preferences.
Choosing a Size for Your Use Case
For home use: If you’re making capsules for yourself and don’t have a strong preference, size "0" is a common starting point because it is smaller than size "00" while still offering useful fill capacity.
For small-batch or business use: Consider the target fill weight, actual powder bulk density, flow properties, and serving size. A lighter, bulkier powder may need the additional volume of size "00".
If you’re not sure: Fill a small test batch to measure the actual weight each capsule size can accommodate and evaluate fill-weight consistency. This is particularly important for lightweight or poorly flowing powders and for products intended for resale.
FAQs
What is the difference between size 0 and size 00 capsules?
Size "00" capsules are larger (approximately 0.95 mL) than size "0" capsules (approximately 0.68 mL). The milligram capacity of either depends on powder density and packing.
Can I use size 00 capsules in a machine made for size 0?
No. Capsule machines are built for a specific capsule size. Match your capsule size to the machine manufacturer’s instructions.
How much powder does a size 0 capsule hold?
A size "0" capsule holds approximately 0.68 mL. For illustration, at a bulk density of 0.8 g/mL, that equals about 540 mg of powder. Actual fill weight must be checked for your formulation.
Is gelatin or vegetarian better for capsules?
Neither is inherently better for every use. Gelatin capsules are animal-derived; vegetarian capsules are generally made with cellulose-derived materials such as HPMC. Check ingredient and equipment compatibility for your application.
What capsule size is best for beginners?
Size "0" is a common starting point because it is smaller than size "00" while still providing useful capacity. Size "00" may be better if your formulation needs more volume per capsule.
Explore our capsule machines and capsules. Browse bulk herbs and spices. Questions? Contact our team.
Author, Monterey Bay Herb Co. Team
Monterey Bay Herb Co. has supplied bulk herbs, botanicals, and herbal supplies since 1997, serving herbalists, formulators, and small businesses across the country.
