MAXScanner biology & lab calculator
DNA Concentration Calculator — A260, Purity Ratios, ng/µL & nM
Convert A260 absorbance to dsDNA, ssDNA or RNA concentration with dilution and path-length correction, inspect A260/A280 and A260/A230 purity ratios, and convert DNA ng/µL to nM when fragment length is known.
Results
Enter A260 ≥ 0, dilution factor > 0 and path length > 0
Formula, example and assumptions
Concentration(ng/µL)=A260×factor×dilution/path length; factors: dsDNA 50, RNA 40, ssDNA 33. dsDNA nM=(ng/µL×10⁶)/(bp×660).
A260=0.5 for undiluted dsDNA at a 1 cm normalized path gives 25 ng/µL.
- Standard A260 factors are approximations and assume an appropriate blank and absorbance measurement.
- Purity ratios are screening indicators, not proof that a sample is suitable for a downstream assay.
Frequently asked questions
Why are ng/µL and µg/mL numerically equal?
One nanogram per microlitre equals one microgram per millilitre because both numerator and denominator scale by 1,000.
What does A260/A280 tell me?
It is commonly used as a quick nucleic-acid purity indicator. Interpret it with your instrument guidance and sample context rather than as a pass/fail result by itself.