1,250
ng/µL
1,250
µg/mL
125,000
ng
125
µg
1,250
ng/µL
1,250
µg/mL
125,000
ng
125
µg
The DNA Concentration Calculator determines the concentration of a DNA sample based on its absorbance at 260 nm using the Beer-Lambert law. Spectrophotometric measurement at 260 nm is the most common method for quantifying nucleic acids in molecular biology laboratories. This calculator supports dsDNA, ssDNA, and RNA extinction coefficients so you can quickly convert your OD readings to concentration values in ng/µL.
This calculator applies the Beer-Lambert law to convert UV absorbance readings to nucleic acid concentration:
Concentration (ng/µL) = A260 × Dilution Factor × Extinction Coefficient
The standard extinction coefficients are:
An A260 reading of 1.0 in a 1 cm path-length cuvette corresponds to approximately 50 µg/mL of double-stranded DNA. The dilution factor accounts for any dilution made before measuring the absorbance.
Inputs
Results
An A260 of 0.5 with a 50-fold dilution gives a dsDNA concentration of 1250 ng/µL (1.25 µg/µL).
Inputs
Results
A direct reading of A260 = 0.25 without dilution corresponds to 12.5 ng/µL of dsDNA.
For reliable results, the A260 reading should be between 0.1 and 1.0 AU. Readings below 0.1 are near the instrument noise floor, while readings above 1.0 may exceed the linear range of the spectrophotometer. Dilute concentrated samples to fall within this range.
The difference arises from hypochromicity. Double-stranded DNA absorbs less UV light per mass than single-stranded nucleic acids due to base stacking interactions. RNA has an intermediate value because it contains significant secondary structure but is predominantly single-stranded.
Measure the A260/A280 ratio. Pure DNA has a ratio of approximately 1.8. A ratio significantly lower indicates protein contamination. Also check the A260/A230 ratio, which should be between 2.0 and 2.2 for clean samples; lower values suggest contamination with organic compounds like phenol or guanidinium salts.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
How helpful was this calculator?
5.0/5 (1 rating)
