DNA Concentration Calculator

How to calculate DNA concentration from A260

1. Choose the type of nucleic acid: double-stranded DNA, single-stranded DNA, RNA or an oligo.
2. Type the A260 reading and the dilution factor. Add A280 and A230 to check purity.
3. The concentration appears in ng/µL with the purity ratios.

Frequently asked questions

What factors are used?

50 ng/µL per A260 unit for double-stranded DNA, 33 for single-stranded DNA and 40 for RNA. For an oligo, the extinction coefficient is worked out from its sequence by the nearest-neighbor method.

What purity ratios should I expect?

An A260/A280 of about 1.8 for DNA and 2.0 for RNA, and an A260/A230 of about 2.0 to 2.2. Lower values suggest protein, phenol or salt.