Short answer: Choose diameter first, based on your target tablet weight — a 500 mg tablet needs meaningfully more die volume than a 200 mg one, and forcing a heavy formula into a small die produces an unusually thick, hard-to-swallow tablet. Then choose shape: round is the default for most supplements and pharma-style tablets, oval and caplet shapes suit larger doses that need to swallow more easily, and square or custom shapes are mostly a branding choice. Finally, confirm the die fits your press — not every press rates every size, so check compatibility before you order.
This is a decision worth making before you buy tooling, not after — installing a die is a five-minute mechanical task, but picking the wrong size or shape means re-buying tooling once you realize the tablet doesn't fit the dose, doesn't swallow well, or doesn't fit your press.
Step 1: Size — Start From Your Target Weight
Die diameter and depth together determine how much powder volume the cavity can hold, which is what your tablet weight is ultimately limited by. If you haven't calculated your target tablet weight yet, see how to calculate tablet weight for a target dose first — that number is what should drive size selection, not the other way around.
As a rough guide:
| Target tablet weight | Typical diameter range |
|---|---|
| Under 200 mg | 6–8mm |
| 200–400 mg | 8–10mm |
| 400–700 mg | 10–13mm |
| 700 mg+ | 13mm+, or a caplet/oval shape to keep thickness reasonable |
These ranges aren't fixed rules — powder density changes how much weight a given volume holds — but they're a reasonable starting point before you calibrate fill depth on the actual press. If your target weight and preferred diameter don't line up well (a small round die forced to hold a heavy dose), that's usually the signal to go up in diameter or switch to an oval or caplet shape rather than just cranking fill depth deeper, which produces an oddly tall, thick tablet that can be awkward to swallow and harder to compress evenly.
Step 2: Shape — Match the Tablet to Its Use
Round. The default choice for most tablets, pharma-style products, and standard supplements. Simple, familiar to swallow, and the easiest shape to work with mechanically — least prone to alignment issues during installation and running. Available with a standard concave face (a light dome, the most common look) or deep concave for a more pronounced curve.
Oval. Presents a smaller cross-section to the throat than a round tablet of the same weight, which is why oval shapes are common for larger doses where swallowability matters more than with a small tablet. Slightly more particular about powder flow during fill than round, since the die cavity isn't symmetric.
Caplet. A capsule-shaped tablet — elongated with radius ends — that swallows like a capsule but presses and packages like a tablet. The standard pick once a dose gets large enough that even an oval starts to feel big, without switching to actual capsule manufacturing.
Square (or other custom shapes). Mechanically similar to round to work with, but chosen almost entirely for differentiation — a distinctive shape for a branded product line, confectionery-style supplements, or shelf standout rather than for any dosing or swallowability reason.
Engraved detail (logos, score lines). Any of the above shapes can be engraved with a logo, imprint code, or score line for splitting the tablet in half. Worth knowing before you order: fine engraved detail is more prone to the picking defect than a plain face, and needs more attention during cleaning to keep residue from building up in the detail over time.
Step 3: Confirm It Fits Your Press
Not every die size is rated for every press — a larger die can physically exceed what a smaller press's tooling head and force output are built for. As an example, our own universal tooling line covers 8–19mm across five stock shapes, but individual presses have their own maximum: the TDP-0 and TDP-5 both handle up to 10mm round dies, while the TDP-1.5 tops out at 8mm — and the largest shapes (16mm oval, 19mm caplet) are TDP-5-only. Always check a die's listed compatibility against your specific press model before ordering, not just its diameter against the general size range advertised.