Capsule Size and Fill Weight for Botanical Powders: The Bulk-Density Math Behind the Dose
Buyer’s snapshot
- Fill weight is shell volume multiplied by the powder’s density. A size 00 shell holds about 450 mg of a powder that settles at 0.50 g/mL, a size 0 about 340 mg and a size 1 about 240 mg. The same dose therefore needs a different number of capsules in each.
- A 500 mg fill of a 0.50 g/mL botanical does not fit a size 00 shell at all. At an 85 percent fill it needs a tapped density of about 0.65 g/mL in size 00, 0.87 g/mL in size 0 and 1.23 g/mL in size 1.
- For a 1,500 mg daily dose at 0.50 g/mL, a 60-count bottle lasts 15 days in size 00, 10 days in size 0 and about 7.5 days in size 1.
- Name the density method on the RFQ and measure on the finished blend. Published shell volumes differ by up to about 5 percent between sources and between gelatin and HPMC shells, so the shell type is confirmed per brief.
- Silk Foods Ceylon (SFC) fills capsules at 100,000 per shift and 200,000 per day under BRCGS and FSSC 22000 V6, with a MOQ of 180 bottles per single shift.
A brand team usually starts with a dose (“500 mg of moringa”) and a bottle (“60 capsules”), and only later learns that the two numbers cannot both be true in the capsule size it wanted. The reason is bulk density. Botanical leaf and root powders are light, and a light powder fills a shell by volume long before it reaches the weight on the label. This piece is for nutraceutical and wellness brand buyers in the US, EU, UK and Australia who are writing a private-label brief and want to check the arithmetic before the first sample.
How do capsule size and bulk density set the fill weight?
Fill weight in milligrams equals the usable shell volume in millilitres multiplied by the powder density in grams per millilitre, times 1,000. Shell volume is fixed by the size number. Density is a property of your powder, so two botanicals filled into the same shell can differ by a factor of two in how much dose each one carries.
A 2026 sizing guide from Vivion, a capsule-supply company, lists approximate maximum volumes of 0.9 mL for size 00, 0.68 mL for size 0, 0.48 mL for size 1 and 0.36 mL for size 2. Other published sheets give slightly different figures: size 00 is commonly shown between 0.90 and 0.95 mL, and size 1 between 0.48 and 0.50 mL. The table below uses the Vivion volumes and three illustrative tapped densities, from a light leaf powder to a denser blend.
| Shell size | Volume (mL) | At 0.40 g/mL | At 0.50 g/mL | At 0.60 g/mL |
|---|---|---|---|---|
| 00 | 0.90 | 360 mg | 450 mg | 540 mg |
| 0 | 0.68 | 272 mg | 340 mg | 408 mg |
| 1 | 0.48 | 192 mg | 240 mg | 288 mg |
| 2 | 0.36 | 144 mg | 180 mg | 216 mg |
These are full-shell figures, the theoretical ceiling. A production fill does not sit at 100 percent, because the powder has to flow into the shell and the two halves have to close without trapping powder at the rim. The worked example below uses 85 percent as a planning assumption. It is not an SFC or SRV figure, and the real number comes from a fill trial on your blend.
The densities in the table are illustrations, not specifications for any particular lot. The shape is the point: halving the density halves the dose a shell can carry.
Which density should you use, bulk or tapped?
Use the density that matches how the filling line packs the powder. The Vivion guide advises loose bulk density for gravity-fed or dosator machines that do not compress the powder, and tapped density for machines with tamping pins or compression. Either way, measure it on the finished blend, including any excipient, because additives can shift density by a large margin.
Bulk density is the mass of an untapped powder divided by its volume, including the air between particles. Tapped density is the higher figure reached after the container is mechanically tapped until the volume stops changing. The United States Pharmacopeia’s general chapter on the topic (the 38th edition text, chapter 616) describes Method I: about 100 g of powder in a 250 mL graduated cylinder, volume read untapped, then read again after 10, 500 and 1,250 taps, with tapping continued until two readings agree within 2 mL. The chapter is harmonised and has been revised since, so the version your quality lab works to should be named on the specification.
A procurement-side observation
Consider a brand that approves a sample at one density and receives a production lot milled a little finer. Nothing is out of specification on moisture or assay, yet the shell now fills to a lighter weight and the label dose is short. A hypothetical, but a common shape. The gap sat in a spec line that was never written: a tapped density range, with the method named. For fill-critical SKUs that one line does more work than a second purity test.
Particle size feeds directly into this. In general, finer milling lowers bulk density and worsens flow, which is why capsule briefs usually name a coarser mesh than beverage briefs. The moringa leaf powder spec for greens blends and capsule SKUs sets out that split for one botanical and why the mesh standard must be named beside the number.
What does the maths look like for a real dose?
Start from the daily dose, divide by the mg a shell can carry at your planning fill, and round up to a whole capsule. The result drives the label’s serving size, the bottle’s days of supply and, through them, the price per day. Take a daily dose of 1,500 mg of a botanical leaf powder that tests at 0.50 g/mL tapped density, with no excipient.
| Shell size | Capacity at 85% fill | Capsules per day | mg per capsule | Shell volume used | Days in a 60-count bottle |
|---|---|---|---|---|---|
| 00 | 383 mg | 4 | 375 mg | 83% | 15 |
| 0 | 289 mg | 6 | 250 mg | 74% | 10 |
| 1 | 204 mg | 8 | 188 mg | 78% | 7.5 |
Three readings follow from the table. First, the shell choice moves the days of supply by a factor of two, and so moves the cost per serving the shopper sees on the shelf. Second, the fill in the smaller shells settles well below 85 percent once the dose is split into whole capsules, which is a signal to check uniformity in the trial, not a reason to resize. Third, the 60-count bottle that looks standard on a shelf sells a very different product depending on the shell behind it.
Now invert the question. If the label says 500 mg per capsule, what density does the powder need?
| Shell size | Usable volume at 85% fill | Tapped density needed for a 500 mg fill |
|---|---|---|
| 00 | 0.765 mL | 0.65 g/mL |
| 0 | 0.578 mL | 0.87 g/mL |
| 1 | 0.408 mL | 1.23 g/mL |
A light leaf powder at 0.50 g/mL cannot deliver 500 mg in a size 00 shell at any sensible fill, because 0.9 mL times 0.50 g/mL is 450 mg even when completely full. The options are a larger shell, a lower dose per capsule with more capsules per serving, or a densified blend. A 3-capsule serving of 500 mg is a 1,500 mg dose, so the 4-capsule row above is the realistic version of the same dose for a leaf powder. Choose the label before the shell, not after, and the dose and the capsule count agree on day one.
How do you build a 60-count bottle around the numbers?
Work from the days of supply you want to print, then check that the capsule count per day is acceptable to the shopper. A 30-day bottle of a 1,500 mg dose at 0.50 g/mL needs 120 capsules in size 00 or 180 in size 0, so a “60-count, 30-day” claim only works if the dose is half that, or the powder is denser than the example.
A short checklist keeps the brief honest:
- Write the dose per day first, with any excipient or flow agent counted in the fill weight.
- Ask for a tapped density range on the sample lot and on a second lot, so you see batch variation before committing.
- Calculate capsules per day for two shell sizes and compare the days of supply.
- Confirm the shell type, gelatin or HPMC, per brief, since shell volume and weight differ slightly between them.
- Run a short fill trial and weigh a sample of filled capsules against the target, not just the first one.
Capsule count also affects the minimum order. SFC sets a MOQ of 180 bottles per single shift, and the capsule contract manufacturing MOQ explainer walks through how bottle count and capsules per bottle turn into a first order. The capacity and batch-size guide covers line capacity, and the private-label capsule timeline shows where the fill trial sits in the calendar.
What should the RFQ line say?
State the fill-critical properties on the request, in a form a supplier can answer with a number. Four lines cover most of it: the daily dose and the capsules per day you can accept, the mesh size with the sieve standard named, the tapped density range with the method named, and the shell type. Without the density line, the supplier quotes against a dose that may not fit the shell.
A workable RFQ block for a botanical capsule reads:
- Product and plant part, for example moringa leaf powder, with the Latin name.
- Target dose per day and maximum capsules per day.
- Particle size, in mesh or microns, with ASTM E11 or ISO 3310-1 named.
- Tapped density, in g/mL, with the method named and a requested range.
- Shell type and size, or “supplier to propose”.
- Packaging: count per bottle, bottle size and closure.
- Documents: certificate of analysis per batch, and any market-specific declarations.
For moringa, the moringa capsules range is a practical starting point, and the botanical supply behind it comes from the same base as the Sri Lankan herbs category. For a similar spec exercise on a multi-ingredient capsule, the triphala capsule formulation guide shows how ratio and particle size feed the same fill-weight calculation.
Where the Silk Route Ventures model doesn’t fit
A brand that wants a fixed dose and a fixed bottle count locked in before any sample has been weighed: density comes from the powder, and no supplier can promise it in advance. A brand that needs a dose per capsule well above what the botanical’s density allows in the shell it has chosen. For those briefs the answer is a larger shell, a split dose, or a different delivery format.
Frequently asked questions
How do I calculate how many milligrams fit in a capsule?
Multiply the shell volume in millilitres by the powder’s density in grams per millilitre, then by 1,000. A 0.68 mL size 0 shell filled with a powder at 0.50 g/mL carries about 340 mg when full. Apply a planning fill of about 85 percent and confirm it with a fill trial, because flow and closure limit real fills.
Should I use bulk density or tapped density for capsule filling?
Use the one that matches the filling line. Loose bulk density suits gravity-fed or dosator machines that do not compress powder, and tapped density suits machines with tamping pins. Measure it on the finished blend, including excipients, and name the method on the RFQ so supplier and buyer read the same number.
Why can’t I get 500 mg of a leaf powder into a size 00 capsule?
A size 00 shell holds about 0.9 mL. At a typical light-leaf tapped density of 0.50 g/mL, that is about 450 mg even when full, so 500 mg is out of reach. At an 85 percent fill the powder would need to be about 0.65 g/mL. A larger shell or a lower dose per capsule solves it.
Does Silk Route Ventures make private-label botanical capsules at low volume?
Yes. Silk Foods Ceylon runs capsules at 100,000 per shift and 200,000 per day in Matale under BRCGS and FSSC 22000 V6, with a MOQ of 180 bottles per single shift. The SRV R&D and NPD team develops custom formulations within 3 to 4 weeks at most, and shell type is confirmed per brief.
How Silk Route Ventures can help
Silk Route Ventures (SRV) manufactures nutraceutical capsules and supplies bulk Ayurvedic and functional botanicals to wellness brands globally. The Silk Foods Ceylon facility in Matale holds BRCGS and FSSC 22000 V6, with USDA Organic and EU Organic on the relevant SKUs. Capsule MOQ is 180 bottles per single shift, samples ship by international courier in 3 to 5 business days, and the R&D and NPD team develops custom blends within 3 to 4 weeks at most. For a new capsule, the useful first step is to send the dose per day, the bottle count and the target market, so the trade desk can propose a shell size and a fill-weight check before the first sample. Contact us to send an inquiry or request a sample.
Sources
- Vivion, How to Use Bulk Density to Select Capsule Sizes (approximate shell volumes for sizes 00, 0, 1 and 2; loose bulk versus tapped density by filling machine type; fill-volume worked example). https://vivion.com/avoid-capsule-sizing-and-shipping-errors-know-bulk-density/ (retrieved 9 October 2026)
- United States Pharmacopeia, General Chapter 616, Bulk Density and Tapped Density of Powders (USP 38 text; definitions and Method I, 250 mL cylinder, 10, 500 and 1,250 taps). https://www.drugfuture.com/Pharmacopoeia/usp38/data/v38332/usp38nf33s2_c616.html (retrieved 9 October 2026)
Written by the Silk Route Ventures Trade Team. Silk Route Ventures (E-Silk Route Ventures Ltd) is a Sri Lankan B2B supply-chain operator for the Food, Beverage, Wellness, and Nutraceuticals sectors. The Silk Foods Ceylon manufacturing arm holds BRCGS and FSSC 22000 V6 certifications. Questions or to request a sample: Contact us or email info@esilkroute.com.lk.