Tailing Factor Calculator

Calculate the USP <621> tailing factor (T) for a chromatographic peak — enter the peak widths at 5% height for an instant symmetry check.

The tailing factor (T), also known as the symmetry factor, describes how symmetrical a chromatographic peak is. An ideal peak is a symmetric Gaussian shape, but factors like column overload, secondary retention mechanisms, or a poorly end-capped stationary phase commonly cause tailing.

This calculator applies the USP General Chapter 621 formula, T = W0.05 / (2f), where W0.05 is the peak width at 5% of its height and f is the distance from the peak’s leading edge to its apex, also measured at 5% height. The result is rounded to two decimal places; USP General Chapter 621 generally recommends T less than or equal to 2.0 for acceptable system suitability.

For the full system suitability picture — tailing factor alongside resolution, precision, and signal-to-noise — see How to Calculate System Suitability in Chromatography.

Peak width at 5% height (min)

Leading-edge-to-apex distance at 5% height (min)

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