DNA Concentration Calculator
Enter your A260 absorbance reading, dilution factor, and nucleic acid type to calculate concentration using standard spectrophotometric conversion factors.
Last updated: September 22, 2026
Frequently asked questions
Why are there different conversion factors for dsDNA, ssDNA, and RNA?
Each type of nucleic acid has a different characteristic absorbance per unit concentration at 260 nm due to differences in base stacking and structure - double-stranded DNA absorbs less per unit mass than single-stranded DNA or RNA because base stacking in the double helix reduces absorbance (hypochromicity). Using the correct factor for your actual sample type is essential for an accurate result.
What if I don't dilute my sample before measuring?
Enter a dilution factor of 1, meaning no dilution - the calculator will use your A260 reading directly. A dilution factor greater than 1 means you diluted the original sample before measuring, and the calculator scales the result back up to reflect the original, undiluted sample's concentration.
How is this different from the Cell Dilution Calculator?
This DNA Concentration Calculator determines the concentration of a nucleic acid sample from a spectrophotometer absorbance reading - it answers 'what concentration do I actually have?' The Cell Dilution Calculator instead answers a different question: given a known stock concentration and a target concentration, how much stock solution and diluent do you need to combine? Use this tool to measure what you have, and the Cell Dilution Calculator to plan how to dilute it to a target concentration.
Does a high A260 reading always mean high DNA purity?
No - A260 absorbance alone measures total absorbance at that wavelength, which can include contaminants like residual protein, phenol, or RNA contamination in a DNA prep, not just the nucleic acid of interest. Purity is typically assessed separately using the A260/A280 ratio (roughly 1.8 for pure DNA, roughly 2.0 for pure RNA) alongside the concentration calculated here.
What's a typical A260 reading for a usable DNA sample?
It varies enormously by application and extraction method - anywhere from very dilute (A260 well under 0.1) to fairly concentrated (A260 of 1 or more) samples can be usable depending on what you need the DNA for. There's no single 'normal' reading; check the concentration requirements for your specific downstream application.
Why does the result show both µg/mL and ng/µL?
µg/mL and ng/µL are numerically equivalent (1 µg/mL = 1 ng/µL), but different labs and protocols commonly report concentration in one or the other - showing both saves a manual conversion regardless of which unit your protocol or downstream application expects.