DNA Concentration Calculator

Estimate double-stranded DNA concentration from spectrophotometry.

How the Math Works

The DNA Concentration Calculator uses the Beer-Lambert Law principle, which states that light absorption is directly proportional to concentration. The formula conc = A260 × factor × dilution multiplies the measured absorbance at 260nm by an experimentally determined factor (typically 50 for double-stranded DNA) and any dilution factor from sample preparation. This calculation determines nucleic acid concentration in nanograms per microliter, converting optical density readings into quantifiable DNA amounts for laboratory work.

Practical Applications

To use this calculator, first measure your DNA sample's absorbance at 260nm using a spectrophotometer. Record the A260 reading, determine the DNA factor based on your sample type (50 for dsDNA, 40 for ssDNA, 55 for RNA), and note any dilution applied during sample preparation. Multiply these three values together to instantly calculate your DNA concentration. For example, an A260 of 0.8 with no dilution and a factor of 50 yields 40 ng/μL of DNA.

Day-to-Day Use

This calculation is essential for molecular biology workflows where precise DNA amounts matter. Researchers use it to prepare templates for PCR reactions, determine if they have enough genetic material for sequencing, verify DNA quality after extraction, and standardize samples for experiments. Without accurate concentration measurements, experiments might fail due to insufficient or excessive DNA, saving both time and expensive reagents while ensuring reproducible research results.

Worked example

A260 0.5, dilution 1 → 25 ng/µL.

FAQ