Capsule sizes are confusing for one simple reason: they run backwards. The more zeros, the bigger the capsule. A size 000 is the largest standard capsule, while a size 5 is tiny.
If you fill your own capsules, picking the right size decides how many capsules you need per dose, how easy they are to swallow, and how fiddly they are to fill. Here's everything you need to choose with confidence.
Capsule size chart
These are typical figures for standard two-piece capsules. Exact numbers vary slightly by manufacturer.
| Size | Approx. volume | Approx. closed length | Common use |
|---|---|---|---|
| 000 | 1.37 ml | 26 mm | Largest standard size; fewer capsules per dose, harder to swallow |
| 00 | 0.91 ml | 23 mm | The most popular size for filling at home |
| 0 | 0.68 ml | 22 mm | Easier to swallow, still holds a useful amount |
| 1 | 0.50 ml | 19 mm | Mid-size |
| 2 | 0.37 ml | 18 mm | Small |
| 3 | 0.30 ml | 16 mm | Small |
| 4 | 0.21 ml | 14 mm | Very small |
| 5 | 0.13 ml | 11 mm | Micro capsules for very small amounts |
How many milligrams does each capsule hold?
This is the question everyone asks — and the honest answer is: it depends on your powder. Capsules are sized by volume, not weight. A light, fluffy powder takes up far more room per milligram than a dense one.
You can estimate it yourself with one multiplication:
Capsule volume (ml) × your powder's density (g/ml) = fill weight (g)
For example, a size 00 capsule (0.91 ml):
- With a light powder around 0.5 g/ml → about 455 mg
- With a dense powder around 0.9 g/ml → about 820 mg
That's nearly double from the same capsule. It's also why two capsules that look equally full can contain very different amounts — and why filling to a target weight on a scale is the only way to make every capsule match.
How to tell which capsule size you have
- Check the packaging or listing. Empty capsules are always sold by size, so the bag or the product page you ordered from will say it.
- Measure a closed capsule. Compare its length to the chart above. A size 00 is roughly 23 mm long; a size 5 is about 11 mm.
- Still unsure? Keep one capsule of each size you own labeled in a small bag so you never have to guess again.
Which size should you choose?
- Size 00 if you want the best balance of capacity and swallowability. It's the default for most people filling at home.
- Size 000 if you'd rather take fewer capsules and don't mind a larger one.
- Size 0 if 00 feels too big to swallow comfortably.
- Size 5 if you only need a very small amount per capsule.
Filling capsules by hand without the mess
Whatever size you use, the hard part of hand-filling is the same: holding a tiny capsule half steady while you fill it, without spilling powder or pinching it out of shape. Small sizes like 0 and 5 are especially fiddly.
Our Capsule Filler Scoop holds the capsule half upright on your scale so you can tare it, fill it and hit your target weight every time. Each scoop fits one size — 000, 00, 0 or 5 — and the Combo Pack includes one of each if you're not sure which you'll use. Orders of $15 or more ship free in the US.