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DNA Calculator

Open a sequence file (txt, fasta or GenBank format) or paste a sequence in the area bellow.

single strand double strand

linear circular

5' hydroxyl 5' phosphate 5' triphosphate


GC content:

Molecular weight:

Molarity of 1 μg/μl solution:

Number of molecules in 1 μg:

Approx. 260 nm extinction coefficient:

A260 of 1 μg/μl solution after 100-fold dilution:

In the following lines, fill in two out of the three fields and click 'Calculate'.


Absorbance and concentration

In a 1 cm cuvette, 260 nm absorbance after dilution by factor corresponds to original concentration of μg/μl.

For the calculation use:
empirical rules predicted extinction coefficient ?

Empirical rules for the relationship between nucleic acid concentration and 260 nm absorbance (OD260)

260 nm absorbance value 1 (alias "1 OD260 unit") corresponds to following concentrations:
  • 50 μg/ml dsDNA
  • 33 μg/ml ssDNA
  • 20 μg/ml ssDNA oligo
  • 40 μg/ml RNA

OD260 units are sometimes used to describe quantities of nucleic acids. One OD260 unit is the amount of nucleic acid that will give 260 nm absorbance 1 after dissolution in 1 ml of solvent.


Molarity, mass and volume

For micromolar concentration dissolve μg in the volume of μl.


Base-pair molarity of dsDNA solutions

For millimolar concentration of base pairs dissolve μg of dsDNA in the volume of μl.

Online DNA calculator

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DNA base pair molarity calculation

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Number of DNA molecules calculation

OD260 calculator


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