Chromatography Retention Factor Calculator

Work out chromatography retention factor instantly with clear inputs, formula shown and shareable results.

About Chromatography Retention Factor Calculator

The retention factor is the distance a spot travels divided by the distance the solvent front travels, so it is always between 0 and 1 and is independent of how long the plate was run. On silica, polar compounds stick to the plate and give low Rf values. Comparing an unknown's Rf to a co-run standard gives a relative retention that survives small changes in plate and solvent.

Formulas

Retention factor

Rf = distance moved by spot / distance moved by solvent front

Relative retention

relative = Rf(sample) / Rf(standard)

Worked example

With the default values below, Chromatography Retention Factor Calculator returns Retention Factor Rf of 0.4375. Change any input above and every figure here is recalculated in your browser.

Inputs used

Distance travelled by the spotminimum 0 cm: 3.5 cm
Distance travelled by the solvent frontminimum 0 cm: 8 cm
Distance travelled by the reference spotminimum 0 cm: 4.5 cm

Results

Retention Factor Rf: 0.4375
Rf Of The Reference Spot: 0.5625
Relative Retention Against The Standard: 0.7778
Interpretation: Mid-range Rf - good separation window

Step by step

1Values used
2Retention factor
3Relative retention
4Retention Factor Rf= 0.4375
5Rf Of The Reference Spot= 0.5625
6Relative Retention Against The Standard= 0.7778
7Interpretation= Mid-range Rf - good separation window

Assumptions and limits

The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is Rf never greater than one?

The spot is carried by the solvent, so it cannot outrun the front. An Rf of 1 means the compound is not retained at all.

What Rf should I aim for?

Around 0.3-0.5 gives the best resolution and is the usual target when choosing a solvent system for a column.