Guides

Lab label size guide

Every label size table on the internet tells you the dimensions. This one also tells you how much text will actually fit in them, measured rather than guessed.

Circumference, not length

The label size a vessel takes is set by how far around it you can go, less a small gap, and by how much of the barrel is straight. Both are usually much less than people expect from looking at the vessel: a 45 mm cryovial has about 28 mm of straight barrel, and a conical tube loses its bottom third to the taper.

That is why the sizes below cluster on a few standards. They are not arbitrary — they are what fits the vessels that laboratories actually use.

Label sizes by vessel

Vessel	Diameter	Circumference	Label size	Also written as
0.2 mL PCR tube	~6 mm	~19 mm	19.1 × 6.4 mm	0.75 × 0.25 in
0.5 mL microtube	~7 mm	~22 mm	19.1 × 9.5 mm	0.75 × 0.375 in
1.5 mL microtube	~8.5 mm	~27 mm	25.4 × 12.7 mm	1 × 0.5 in
2 mL cryovial	~12.5 mm	~39 mm	28.6 × 12.7 mm	1.125 × 0.5 in
15 mL conical	~17 mm	~53 mm	38.1 × 19.1 mm	1.5 × 0.75 in
50 mL conical	~30 mm	~94 mm	63.5 × 38.1 mm	2.5 × 1.5 in
Microscope slide	25 mm wide	n/a (flat)	25.4 × 19.1 mm	1 × 0.75 in
Reagent bottle	~70 mm	~220 mm	50.8 × 25.4 mm	2 × 1 in
Media bottle	~70 mm	~220 mm	76.2 × 50.8 mm	3 × 2 in

Nominal dimensions for standard laboratory plasticware. Check yours where the fit is marginal.

Original data: how much text fits at each size

Type size	Lines	Plex Sans	Barlow Condensed	Atkinson Hyperlegible	Plex Mono	Space Mono	Courier Prime
4.5 pt	12	64	88	64	51	50	51
5 pt	11	57	79	58	46	45	46
6 pt	9	48	66	48	38	37	38
7 pt	8	41	56	41	32	32	32
8 pt	7	36	49	36	28	28	28
10 pt	5	28	39	29	23	22	23

Measured on a 50.8 × 25.4 mm reagent label. Every template page carries the same measurement for its own size. Figures are characters per line, for 50.8 × 25.4 mm. Measured against the string “Tris-HCl 1 M pH 8.0 25 mg/mL 2026-08-24 GS lot B-204 store 4 C”, which is representative of laboratory text rather than of prose.

How these numbers were produced

Character counts are measured, not estimated. Each figure is the usable label width — the label less the 1 mm safe area on each side — divided by the mean advance width of a representative line of laboratory text, taken from the actual font file with kerning applied.

The sample text matters more than it looks. Laboratory text is unusually dense in digits, decimal points, units and short tokens, and those are narrower than average prose in most typefaces. Measuring with prose, or with the traditional lowercase “n”, understates what fits by a noticeable margin. The string used is “Tris-HCl 1 M pH 8.0 25 mg/mL 2026-08-24 GS lot B-204 store 4 C”.

Line counts are the usable height divided by the editor's default line spacing of 1.18 × type size. Both figures are upper bounds for a single block filling the label; a real design with two or three separate blocks will fit somewhat less.

Common questions

What is the most common lab label size?: 25.4 × 12.7 mm (1 × 0.5 inch) for 1.5 mL tubes, and 50.8 × 25.4 mm (2 × 1 inch) for reagent bottles. Between them they cover most of what a laboratory labels.
How many characters fit on a cryovial label?: About 26 per line at 6 pt on a 28.6 × 12.7 mm label, over four lines — in the default typeface. A condensed face takes that to roughly 36.
Should I use a smaller type size to fit more?: Change the typeface first. A condensed face at 6 pt fits more than the default at 5 pt and stays far more readable through frost and gloves.

Last reviewed 2026-08-24.