Resolution Calculator

Calculate chromatographic resolution (Rs) between two adjacent peaks per USP <621> — enter retention times and peak widths for an instant Rs value.

Resolution (Rs) measures how well two neighboring chromatographic peaks are separated from each other. It’s one of the core system suitability parameters checked before any HPLC method is used for sample analysis, and it directly determines whether closely eluting compounds can be reliably quantified.

This calculator applies the USP General Chapter 621 formula, Rs = 2(tR2 - tR1) / (W1 + W2), where tR1 and tR2 are the retention times of the two peaks and W1/W2 are their baseline widths. The result is rounded to two decimal places, matching how USP acceptance criteria (e.g. “Rs greater than or equal to 1.50”) are conventionally stated.

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

Retention time of peak 1 (min)

Retention time of peak 2 (min)

Peak width of peak 1 (min)

Peak width of peak 2 (min)

Enter values above to see your result.