Size 0 and size 00 are the two most popular empty hard gelatin capsule sizes in the world. They look almost identical in the hand, but size 00 holds about a third more powder. Here is exactly how they differ, how much each one holds, and how to decide which is right for your product.
The short answer
A size 0 capsule holds 0.68 mL, about 544 mg of a typical powder blend (0.8 g/mL), and is the usual choice for doses around 500 mg. A size 00 capsule holds 0.90 mL, about 720 mg of the same blend, and suits higher doses of 600 to 750 mg. Size 00 is 1.8 mm longer and about 0.9 mm wider, so size 0 is easier to swallow.
Size 0 vs size 00 at a glance
| Specification | Size 0 | Size 00 |
|---|---|---|
| Closed length | 21.6 mm (0.850 in) | 23.4 mm (0.921 in) |
| Cap outer diameter | 7.64 mm | 8.56 mm |
| Body outer diameter | 7.35 mm | 8.23 mm |
| Nominal volume | 0.68 mL | 0.90 mL |
| Fill at 0.6 g/mL | about 408 mg | about 540 mg |
| Fill at 0.8 g/mL | about 544 mg | about 720 mg |
| Fill at 1.0 g/mL | about 680 mg | about 900 mg |
| Empty shell weight | about 99 mg | about 123 mg |
| Capsules per kg | about 10,101 | about 8,130 |
All figures are from our empty capsule size chart, which lists every size from 000 to 5.
How much more does a size 00 capsule hold?
A size 00 capsule holds 0.90 mL against 0.68 mL for size 0, which is about 32 percent more volume. In practice that means roughly 175 mg more fill for a typical powder at 0.8 g/mL. If your dose sits just above what a size 0 can take, moving up to size 00 is usually simpler than reformulating to make the blend denser.
Fill weight depends on your powder, not just the size
Capsules are specified by volume. The weight they hold depends on the bulk density of your blend. A light, fluffy herbal powder at 0.5 g/mL fits only about 340 mg into a size 0, while a dense mineral blend at 1.2 g/mL fits over 800 mg into the same shell. That is why the right first step is always to measure the tapped bulk density of your final blend.
Also plan to fill to about 90 percent of the nominal volume rather than to the brim. That leaves room for the blend to settle and for the cap to close cleanly on an automatic filling machine.
Which one should you choose?
Choose size 0 when
your dose fits comfortably, typically up to about 500 mg of a standard blend. Size 0 is easier to swallow, uses less gelatin per capsule and is the most widely used size for medicines and supplements.
Choose size 00 when
your dose is roughly 600 to 750 mg, or your blend is light and bulky. Size 00 is still comfortable for most adults and avoids splitting the dose into two capsules.
Consider two capsules when
even size 00 is not enough. Two size 0 capsules are often easier to swallow than one size 000, and give flexible dosing.
Swallowing and patient comfort
Size 00 is generally regarded as the largest size most adults swallow comfortably every day. If your product is for children, elderly patients or people who struggle with pills, size 0 or smaller is the safer choice. A smooth, glossy gelatin shell helps either size go down easily.
Filling machines and change parts
Capsule sizes are an international standard, so size 0 and size 00 capsules from any compliant manufacturer run on the matching size tooling. Switching between the two needs the correct change parts (bushes and segments) on your filling machine, so check what your line is set up for before you decide.
Frequently asked questions
Is size 00 bigger than size 0?
Yes. Capsule numbers run backwards, so 00 is larger than 0. A size 00 capsule is 23.4 mm long and holds 0.90 mL; a size 0 is 21.6 mm long and holds 0.68 mL.
How many mg does a size 0 capsule hold?
About 544 mg of a powder with a bulk density of 0.8 g/mL, and about 680 mg at 1.0 g/mL. The exact weight depends on your blend.
How many mg does a size 00 capsule hold?
About 720 mg at a bulk density of 0.8 g/mL, and about 900 mg at 1.0 g/mL.
Which size is best for a 500 mg dose?
For most blends, size 0. It holds about 544 mg at 0.8 g/mL. If your powder is light and bulky, size 00 may be needed.
Do you supply size 0 and size 00 capsules?
Yes. Size 0 is in regular production at Universe Capsules, and size 00 is available on request in plain, printed, metallic and pearl finishes.
Not sure which size fits your formulation?
Send us your fill weight and bulk density and we will recommend a size, then supply samples so you can test them on your own filling line.
Ask for a size recommendation
