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Centimeters to Inches Converter

↔ Convert in to cm instead

Common Conversions

cm in
0.5 0.197
1 0.394
2 0.787
2.54 1
5 1.969
10 3.937
15 5.906
20 7.874
25 9.843
30 11.811
50 19.685

Why this conversion matters in chemistry

A standard 1 cm spectroscopy cuvette path length works out to 0.394 inches on a machine-shop drawing; a 15 cm Buchner funnel is 5.9 inches; a 30 cm bench section is just under a foot. The bridge is dividing by 2.54, the exact 2.54 cm per inch factor pinned by international agreement. Most of chemistry happens in metric — glassware, bench measurements, pipetted volumes — so the direction that matters in practice is when a metric specimen has to be described for a US-built fabrication or a compression fitting sized in imperial units. Once the number is in inches, the downstream calculation usually stays imperial until the result loops back to chemistry.

Formula

in = cm ÷ 2.54

Worked Examples

2.54 cm = 1 in

The defining anchor. Exact by international agreement.

1 cm = 0.3937 in

A standard UV-Vis spectroscopy cuvette path length. Worth keeping in mind when absorbance units don't quite line up with published molar extinction coefficients.

15 cm = 5.906 in

A typical Buchner funnel diameter. Close enough to 6 inches that the US-imperial and metric versions of the same glassware are often interchangeable.

30 cm = 11.811 in

Roughly one foot, though not exactly — the foot is precisely 30.48 cm. Useful for sanity-checking a bench layout without pulling out a ruler.

Frequently Asked Questions

How do I convert cm to inches?
Divide by 2.54. So 15 cm is 5.906 inches, 30 cm is about 11.8 inches. The factor is exact by definition, so the result is as precise as your input.
What's 1 cm in inches?
0.3937 inches — a little less than 2/5 of an inch. Useful rough shortcut: 10 cm is about 4 inches, which gets you within 1.5%.
When does this conversion come up?
Mostly when ordering US-manufactured lab equipment sized in imperial units, or when a metric dimension has to cross over to a US fabricator. Tubing, fittings, column hardware, and a fair amount of custom glassware all sit on the seam between the two conventions.
What lab items are typically sized in inches?
NPT pipe fittings, compression-style gas fittings, some column hardware, older US-manufactured glassware, and anything built by a US machine shop. Once you're on the bench and measuring volumes or lengths, though, the rest of chemistry defaults to metric.