What is chromatographic resolution (Rs)?

Resolution (Rs) is a dimensionless number describing how well two adjacent peaks are separated. Rs = 1.0 means ~2% overlap; Rs ≥ 1.5 is considered baseline separation with <0.1% overlap.

What is the formula for resolution?

Rs = 2(tₑ₂ − tₑ₁) / (w₁ + w₂) for baseline widths. For half-height widths, substitute w½ values and apply a factor: Rs = 1.18(tₑ₂ − tₑ₁) / (w½₁ + w½₂).

What is a good resolution value?

Rs < 1.0: peaks overlap significantly. Rs = 1.0: ≤2% overlap (usable for quantitation with corrections). Rs ≥ 1.5: baseline resolution, ideal for most analytical work. Rs ≥ 2.0: excellent separation.

What is the difference between baseline width and half-height width?

Baseline width (w) is measured at the base of the peak by tangent lines and equals ≈4σ. Half-height width (w½) is the width at 50% peak height and equals ≈2.355σ. Both are valid; the formula uses a factor of 2 for baseline and 1.18 for half-height.

Which peak should be entered as peak 1 vs peak 2?

Peak 1 should be the peak that elutes first (smaller retention time). Peak 2 is the later-eluting peak. The calculator will flag them if entered in the wrong order.

Resolution Chromatography Calculator

Enter retention times and peak widths for two analyte peaks to calculate chromatographic resolution (Rs).

Peak Parameters

Peak Width Measurement Method

Baseline width (w) Half-height width (w½)

Peak 1 (first-eluting)

Retention Time t_R1

min

Width w₁

min

Peak 2 (second-eluting)

Retention Time t_R2

min

Width w₂

min

Resolution Rs

—

Resolution Quality Guide

Rs < 1.0 Overlapping peaks

Rs = 1.0 ~2% overlap

Rs = 1.5 Baseline resolution

Rs ≥ 2.0 Excellent separation

Summary

This calculator computes chromatographic resolution (Rs) between two adjacent peaks using the standard USP/ICH formula. Enter the retention times and peak widths for both peaks and instantly see the Rs value along with a quality rating. Supports both baseline-width and half-height-width measurement methods, covering HPLC, GC, and TLC applications.

How it works

Enter the retention time for the first peak (tₑ₁).
Enter the retention time for the second peak (tₑ₂).
Choose peak width method: baseline width (w) or half-height width (w½).
Enter the peak widths for both peaks.
Read the resolution Rs and quality interpretation instantly.

Use cases

Evaluate HPLC method development to ensure baseline separation.
Assess GC column performance for closely eluting compounds.
Compare column efficiency before and after optimization.
Validate analytical methods for regulatory submissions.
Determine whether two peaks are adequately resolved in a chromatogram.
Teach or study chromatography fundamentals and resolution theory.

Frequently Asked Questions

Last updated: 2026-06-11 · Reviewed by Nham Vu