Tools
Label size calculator
Label size on a tube is set by circumference, not by the tube's length. Two numbers give you the answer.
The arithmetic
The maximum label width that will wrap a cylindrical vessel is its circumference — diameter × π — less a gap so the ends do not overlap. A 2–3 mm gap is right for most vessels: enough that a small placement error does not create a step, small enough that the label still looks deliberate.
The maximum height is the straight, unribbed run of the barrel, which is usually well short of the vessel's overall length. On a cryovial the straight run is around 28 mm against a 45 mm vial; on a conical tube the taper takes the bottom third.
Common vessels, measured
| Vessel | Diameter | Circumference | Straight run | Label |
|---|---|---|---|---|
| 0.2 mL PCR tube | ~6 mm | ~19 mm | ~7 mm | 19.1 × 6.4 mm |
| 0.5 mL microtube | ~7 mm | ~22 mm | ~14 mm | 19.1 × 9.5 mm |
| 1.5 mL microtube | ~8.5 mm | ~27 mm | ~18 mm | 25.4 × 12.7 mm |
| 2 mL cryovial | ~12.5 mm | ~39 mm | ~28 mm | 28.6 × 12.7 mm |
| 15 mL conical | ~17 mm | ~53 mm | ~45 mm | 38.1 × 19.1 mm |
| 50 mL conical | ~30 mm | ~94 mm | ~75 mm | 63.5 × 38.1 mm |
| 250 mL bottle (GL45) | ~70 mm | ~220 mm | ~90 mm | 76.2 × 50.8 mm |
Custom sizes
The editor takes any size in millimetres or inches and stores it in integer micrometres, so a size entered as 28.6 mm is 28,600 µm exactly and prints as such. There is no snapping to a preset and no rounding to a printer's dot grid until output.
Entering a custom size also updates the “fits” indicator, which names the stock vessels that size will still wrap. It is an authoring aid rather than a guarantee, and it is derived from the same circumference figures in the table above.
Common questions
- How do I calculate label width for a round tube?
- Diameter × π, then subtract 2–3 mm so the ends do not overlap. For a 12.5 mm cryovial that is about 39 mm around and a 28–36 mm label, depending on how much of the barrel is straight.
- Why is the label shorter than the tube?
- Because only the straight part of the barrel takes a rectangular label. Tapers and moulding ridges make the label bridge, and a bridged edge lifts.
Last reviewed 2026-08-24.