OD260 to Nucleic Acid Concentration Calculator

Spectrophotometers measure nucleic acid concentration by reading light absorbance at 260 nm (OD260) — the OD260 to Nucleic Acid Concentration Calculator converts that raw absorbance reading into a usable concentration value. Enter your OD260 reading, select your nucleic acid type (dsDNA, ssDNA, RNA, or oligonucleotides), and provide your path length and dilution factor to get your sample's nucleic acid concentration in both µg/mL and ng/µL, plus the extinction coefficient applied.

Absorbance reading from spectrophotometer at 260nm

cm

Cuvette path length (standard is 1 cm)

Factor by which sample was diluted (1 = no dilution)

Results

Nucleic Acid Concentration

--

Concentration

--

Extinction Coefficient Used

--

More Biology Tools

Frequently Asked Questions

What are the standard extinction coefficients for different nucleic acids?

The standard extinction coefficients are: dsDNA = 50 µg/mL per OD260, ssDNA = 40 µg/mL per OD260, RNA = 40 µg/mL per OD260, and oligonucleotides = 33 µg/mL per OD260. These are approximations as the exact values depend on sequence composition.

Why is OD260 used to measure nucleic acid concentration?

Nucleic acids have maximum absorbance at 260nm due to the aromatic bases in their structure. This makes OD260 the standard wavelength for quantifying DNA and RNA concentrations using spectrophotometry.

What is the difference between µg/mL and ng/µL units?

These units are equivalent: 1 µg/mL = 1 ng/µL. Both are commonly used in molecular biology, with ng/µL often preferred for smaller sample volumes typical in PCR and sequencing applications.

How does dilution factor affect the calculation?

The dilution factor accounts for any dilution made to the original sample before measurement. If you diluted your sample 1:10, the dilution factor is 10, and the calculator multiplies the result by this factor to give the original concentration.

What path length should I use for standard cuvettes?

Standard spectrophotometer cuvettes have a 1 cm path length. Some microvolume spectrophotometers use shorter path lengths (0.2-1.0 mm), so always check your instrument specifications and adjust accordingly.

How accurate are these concentration calculations?

These calculations provide approximations based on average extinction coefficients. The actual values can vary by ±20% depending on the specific sequence composition, salt concentration, and pH of your sample.

What OD260 range is optimal for accurate measurements?

Most spectrophotometers are most accurate in the OD260 range of 0.1-1.0. Readings below 0.1 may have poor signal-to-noise ratio, while readings above 1.0 may exceed the linear range and require dilution.