Calculate resolution between two peaks, or predict the plate count needed for a target resolution.
From Peak Data: Enter the retention times and base widths of two adjacent peaks. The calculator computes resolution directly. Use the same time units for all values.
From N, α, k: Use this when you want to predict resolution from column parameters — useful for method development. Enter plate count (N), selectivity factor (α = k₂/k₁), and average retention factor (k).
Direct calculation: Rs = 2(tR2 − tR1) / (Wb1 + Wb2). This is the standard USP definition of resolution.
Fundamental equation: Rs = (√N/4) × ((α−1)/α) × (k/(1+k)). This separates resolution into three independent contributions: efficiency (N), selectivity (α), and retention (k). It shows that the most efficient way to improve resolution is usually to increase α (change stationary phase, mobile phase composition, or pH), rather than increasing N (longer column, slower flow).
Worked example: Peak 1 elutes at 5.2 min (Wb = 0.25 min), Peak 2 at 5.8 min (Wb = 0.28 min). Rs = 2(5.8−5.2)/(0.25+0.28) = 1.2/0.53 = 2.26. Baseline resolved.
Scaling rule: Resolution scales with √N. To double the resolution, you need 4× the plate count (4× column length at constant HETP). This is why improving selectivity is almost always preferred over brute-force efficiency increases.