Calculator

Path Length Calculator: Find the Right Cuvette Path Length

Compute the ideal path length from the Beer-Lambert law — enter absorbance, extinction coefficient and concentration.

Path Length Calculator (Beer-Lambert)

Enter your target absorbance, molar extinction coefficient and concentration to find the right path length. Standard cells: 0.1 – 100 mm.

Common analyte preset (optional)Target absorbance A (typically 0.2 – 1.5)Extinction coefficient ε (L·mol⁻¹·cm⁻¹)Concentration c (mol/L)

How to Use This Calculator

The Beer-Lambert law — A = ε · c · l — links absorbance (A), molar extinction coefficient (ε), concentration (c) and path length (l). Measurements are most reliable between A = 0.2 and 1.5; below that noise dominates, above that stray light and non-linearity creep in. Rearrange to l = A / (ε·c) and you get the path length that puts your sample in the sweet spot.

Which Cell to Choose

Path length	Use case	scuvette option
0.1 – 1 mm	Highly concentrated samples, high ε chromophores	ultra-micro cells
2 – 5 mm	Concentrated samples, sub-micro volumes	micro cells
10 mm (standard)	Routine UV-Vis, most assays	10 mm standard cells
20 – 100 mm	Trace analysis, very dilute samples	long-path cells

If your calculated path length falls between standards (e.g. 7 mm), choose the next shorter standard and dilute slightly, or the next longer and concentrate — whichever keeps your absorbance between 0.2 and 1.5.

Not sure what to measure your sample at?
Send us your instrument model and sample type — our engineers will reply within 1 business day with the right specification and a firm price. Contact Scuvette →

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