Under Article 6 of the Enforcement Decree of the Seal Certification Act, a seal eligible for registration must measure between 7 mm and 30 mm on each side. Outside that range it cannot be registered.
Common sizes by purpose
- Around 10 mm — personal everyday seal, small enough for tight margins.
- Around 15 mm — the most common size for a registered seal.
- Around 18 mm — corporate round seal, larger because the company name has to fit.
- 21–30 mm — address stamps and large company seals.
What mm means for an image
Images have no millimetres of their own; they get a physical size only when paired with a resolution. One inch is 25.4 mm, so 15 mm at 300 dpi works out to 15 ÷ 25.4 × 300 ≈ 177 pixels. BaroStamp does that arithmetic for you and shows the pixel size alongside.
Which resolution to pick
150 dpi is fine for screen-only documents. Choose 300 dpi for anything printed, or 600 dpi if the seal will be enlarged. Raising the resolution does not change how big it looks on screen — only the file size.