Making gel capsules at home is straightforward with the right equipment: you need empty capsules, a manual filling machine, your powdered ingredient, and a clean workspace. The whole process takes about 15 to 30 minutes once you get the hang of it, and a basic manual machine can fill 24 to 100 capsules at a time.
Choosing Your Capsule Material
Empty capsules come in two main types: gelatin and HPMC (hydroxypropyl methylcellulose). Gelatin capsules are made from animal-derived protein and are the traditional choice. HPMC capsules are plant-based, making them suitable for vegetarian or vegan use and compatible with most religious dietary restrictions.
In terms of performance, the two are very similar. Both dissolve and release their contents at comparable rates, though gelatin capsules tend to disintegrate slightly faster on an empty stomach. The biggest practical difference is moisture sensitivity. Gelatin shells need 12% to 16% moisture content to stay flexible, so they can become brittle in dry environments or sticky in humid ones. HPMC shells contain only 2% to 6% moisture and are far more resilient, holding up well even in dry conditions. If you live somewhere with fluctuating humidity, HPMC capsules are more forgiving to store.
Picking the Right Capsule Size
Capsule sizes are numbered, and the numbering runs counterintuitively: the larger the number, the smaller the capsule. Size 00 is the most popular for home use because it holds a meaningful dose without being too large to swallow. Here’s what each size holds by volume and approximate powder weight:
- Size 000: 1.37 ml, roughly 820 to 1,370 mg of powder
- Size 00: 0.90 ml, roughly 540 to 900 mg
- Size 0: 0.68 ml, roughly 410 to 680 mg
- Size 1: 0.48 ml, roughly 290 to 480 mg
- Size 2: 0.36 ml, roughly 215 to 360 mg
- Size 3: 0.27 ml, roughly 160 to 270 mg
- Size 4: 0.20 ml, roughly 120 to 200 mg
Those weight ranges depend on how dense your powder is. A fluffy, lightweight powder like marshmallow root will land near the low end, while something dense like magnesium oxide will fill toward the high end. To figure out which size you need, divide your target dose by the approximate capacity and see if it fits in one capsule or if you’ll need two per serving.
Using a Filler to Get Consistent Doses
If your dose of active ingredient doesn’t completely fill the capsule, you’ll want to add an inert filler to take up the remaining space. This prevents the powder from shifting around loosely inside the capsule and helps keep each dose uniform. Common fillers for home use include rice flour, microcrystalline cellulose (sold as a supplement-making supply), and calcium carbonate. These add bulk without affecting how the active ingredient works in your body.
To calculate how much filler you need, weigh out a single dose of your active ingredient, then weigh the amount of filler it takes to fill one capsule completely. The difference is your filler amount per capsule. Mix the active ingredient and filler thoroughly in a bowl before you start filling. The more evenly blended the mixture is, the more consistent each capsule will be.
Step-by-Step Filling With a Manual Machine
A manual capsule filling machine is an inexpensive tool (typically $20 to $50) with two interlocking trays, a spreader card, and a tamping tool. Here’s the process from start to finish.
First, separate your empty capsules. Each capsule has a longer body (the bottom half) and a shorter cap (the top half). Place the bodies into the bottom tray of the machine and set the caps aside in the top tray. Most machines have holes sized so the capsules drop in with the open end facing up.
Next, pour your pre-mixed powder over the tray of capsule bodies. Use a spreader card or the back of a butter knife to push the powder across the tray, working it into each capsule. Don’t rush this step. Slow, even passes distribute the powder more uniformly than dumping it all at once.
Now tamp the powder down. Use the tamping tool that came with your machine (or a flat piece of acrylic cut to size) and press it evenly across the capsule openings. This compresses the powder so you can fit more in. Research on capsule filling shows that the first two or three tamping rounds do nearly all the work of compacting the powder, after which additional tamping doesn’t meaningfully increase density. So tamp two or three times, adding more powder between each round, until the capsules are full.
Finally, align the cap tray over the body tray and press them together firmly to lock each capsule closed. You’ll feel or hear them click shut. Release the filled capsules from the machine, and brush off any excess powder with a clean cloth.
Filling Capsules With Oils or Liquids
You can also fill hard capsules with oils, tinctures, or other liquids, though it requires a different approach. Use a small blunt-tip syringe or dropper to carefully inject the liquid into each capsule body. Work slowly to avoid overfilling, since any liquid that coats the rim can prevent the cap from sealing properly and cause leaks.
Gelatin capsules handle oils reasonably well, but they will eventually soften if the liquid is water-based. For oil-based fills like fish oil or herbal extracts in carrier oil, gelatin works fine as long as you plan to use the capsules within a few weeks. Close each capsule immediately after filling so the liquid doesn’t have time to weaken the shell walls. Store liquid-filled capsules upright while they set, and keep them in a cool place.
Keeping Everything Clean
Before and after each filling session, wipe down all surfaces of your machine and any tools that contact the powder. A cloth dampened with 70% isopropyl alcohol works well for sanitizing the trays and tamping tool. After cleaning, let everything dry completely before putting it away or starting a new batch. Leftover moisture on the trays can cause capsules to stick or swell, and it creates conditions for microbial growth over time.
If you’re switching between different supplements, thorough cleaning between batches is essential to prevent cross-contamination. Disassemble the machine fully, wipe each component, and inspect the capsule holes for residual powder before reloading.
Storing Your Finished Capsules
Proper storage keeps your capsules from cracking, sticking together, or losing potency. The ideal conditions are 68°F (20°C) at about 50% relative humidity. The acceptable range stretches from 60°F to 75°F and 40% to 60% humidity.
If humidity drops below 40%, gelatin capsules lose moisture and become brittle. They’ll crack or shatter under light pressure. If humidity climbs above 60%, they absorb moisture, soften, and can stick together in clumps. Temperature cycling is equally damaging: moving capsules between warm and cool environments causes condensation inside the container, which pulls moisture out of the shells and deforms them.
Store finished capsules in an airtight glass jar or a sealed plastic container, away from direct sunlight. A cool, dark cabinet works well for most homes. If you’ve made a large batch, consider dividing them into smaller containers so you’re not repeatedly exposing the whole supply to air every time you open the lid. Properly stored gelatin capsules typically hold up for several months, and HPMC capsules are even more stable due to their lower moisture dependence.