Tools
Barcode lab labels
A linear barcode needs length. A tube does not have length. That single fact decides most laboratory barcode questions before anything else does.
Why 2D wins on small vessels
A Code 128 barcode encoding ten characters needs roughly 40 mm of length at a readable bar width, plus quiet zones. A 1.5 mL tube offers about 26 mm of usable circumference, and a curved surface at that — a linear barcode wrapped around a tube presents its bars at continuously varying angles, and the reader sees a distorted image.
A 2D code of the same payload occupies about 10 mm square, which fits, and its error correction tolerates the curvature and the frost. This is why the laboratory world standardised on 2D data matrix codes for tube bottoms and why QR is the pragmatic choice for anything printed in-house.
None of that rules out a linear barcode on a larger vessel. A 50.8 × 25.4 mm bottle label, a 76.2 × 50.8 mm media label or a 99.1 × 38.1 mm sheet label all have the length a Code 128 needs, and if the scanners and the LIMS on your bench already expect a linear code, that is the code to print. The editor generates one: add a barcode block, type the identifier, and it is encoded on your device.
Space needed for ten characters
| Symbology | Footprint | Fits a 1.5 mL tube? | Curvature tolerance |
|---|---|---|---|
| Code 128 (linear) | ~40 × 8 mm | No | Poor |
| Code 39 (linear) | ~55 × 8 mm | No | Poor |
| QR (Model 2, M) | ~10 × 10 mm | Yes | Good |
| Data Matrix | ~8 × 8 mm | Yes | Good |
Making a code scan first time
- Keep the quiet zone
- Four modules of blank space on every side. Crowding a code with text is the most common in-house scanning failure.
- Print black on white
- Inverted or coloured codes work on some readers and not others. On a lab label there is no upside.
- Place it flat
- On a tube, put the code on the part of the wrap that faces out when the tube sits in its rack, so it is never read across the seam.
- Test the actual printer
- A code that scans from the screen proves nothing about a 203 dpi thermal print on a curved surface. Print one, scan it cold, then commit to the design.
Common questions
- Can I print a Code 128 barcode on a lab label?
- Yes. Add a barcode block, enter the identifier, and it is encoded on your device with the check symbol and both quiet zones, then printed at the size you designed. On a 1.5 mL tube it will not fit — ten characters need around 40 mm of straight, flat length — and the editor tells you that rather than printing something unscannable. On a bottle or a sheet label it fits with room to spare.
- QR or Data Matrix?
- Data Matrix is slightly denser and is what commercial pre-barcoded tubes use. QR is more universally readable by phones and general-purpose scanners, which matters more when the codes are printed and read in-house.
Open it in the editor
The editor loads at 38.1 × 19.05 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 2026-08-24.