Label stock
19.05 × 6.35 mm labels
One line, sixteen characters. At this size the question is not what to put on the label but what to keep off it.
Why the size is this and not larger
A 0.2 mL PCR tube has roughly a 6 mm barrel, and most of that barrel is conical. The straight portion that a label can lie flat against is a band a few millimetres deep near the top, which is where 6.35 mm comes from — a quarter of an inch, and about as much as the tube offers before the taper starts pulling the label away from the wall.
Width is limited differently. 19.05 mm is not the circumference of the tube; it is a flag length. Labels at this size are usually applied as a flag, wrapped back on themselves so the printed face stands proud of the tube, because a tube this small has nowhere near enough circumference to carry readable text around it.
What this size is
- In inches
- 0.75 × 0.25 in. An inch size by origin: 19.05 × 6.35 mm is the exact conversion of it, with nothing rounded.
- Vessels it wraps
- Anything from a 1.5 mL microcentrifuge tube upwards, so also a 2 mL cryovial, a 50 mL conical tube and a GL45 reagent bottle. The tightest of those has a usable band of about 26 × 13 mm, which this label fits inside.
- Die-cut sheets
- No stock sheet in the editor is cut to this size. On plain paper it packs 450 per A4, 420 per Letter, cut by hand along printed marks.
- Roll stock that carries it
- 25.4 mm, 38.1 mm, 50.8 mm, 57 mm, 62 mm, 76.2 mm, 101.6 mm. The narrowest that takes it is 25.4 mm, and a roll narrower than the label is reported as an error rather than trimmed.
What fits on a 19.05 × 6.35 mm label
| Type size | Lines | Plex Sans | Barlow Condensed | Atkinson Hyperlegible | Plex Mono | Space Mono | Courier Prime |
|---|---|---|---|---|---|---|---|
| 4.5 pt | 2 | 22 | 30 | 22 | 17 | 17 | 17 |
| 5 pt | 2 | 20 | 27 | 20 | 16 | 15 | 16 |
| 6 pt | 1 | 16 | 23 | 16 | 13 | 13 | 13 |
| 7 pt | 1 | 14 | 19 | 14 | 11 | 11 | 11 |
| 8 pt | 1 | 12 | 17 | 12 | 10 | 9 | 10 |
| 10 pt | 1 | 10 | 13 | 10 | 8 | 7 | 8 |
What to do instead of shrinking the type
- Label the strip, not the tubes
- An eight-tube strip is one object until it is cut. One label on the strip, or on the rack position, carries far more than eight labels on eight tubes ever could.
- Put the identifier on the cap
- Cap labels are round and small, but they are read from above, which is how tubes in a rack are actually read. The barrel label then only has to confirm what the cap says.
- Use a code, not a description
- At sixteen characters a well name and a plate id fit; a sample description does not. Keep the description in the plate map, keyed by what is on the tube.
- Do not go below 4.5 pt
- The editor will not set type smaller than 4.5 pt, because below that a 203 dpi thermal head has fewer than six dots of stroke height to work with and the characters close up. If the text does not fit at 4.5 pt, the text is wrong for the label.
Common questions
- Can I fit a barcode on a 19.05 × 6.35 mm label?
- Not a useful one. A QR code needs a square, and the square available here is 6.35 mm less the safe area — around 4 mm, which at 203 dpi is about 32 dots across. That is too few modules for anything but the shortest payload, and a scanner reading a curved 6 mm tube will struggle regardless. Put the code on the rack or the plate.
- Is this the same as a cryo straw label?
- No. Cryo straw labels are narrower still and are usually printed on the straw itself or on a sleeve. This size is for PCR tubes, strips and small flag applications where a printed face can stand clear of the vessel.
Open it in the editor
The editor loads at 19.05 × 6.35 mm with a worked example in place. It runs entirely in your browser: nothing you type is uploaded, and there is no account to make.
Last reviewed 2026-09-13.