Biology
DNA / RNA Concentration Calculator
Convert an A260 absorbance reading into nucleic-acid concentration and check sample purity from the 260/280 ratio.
Your inputs
Change any value to update the result instantly.
Concentration
25 µg/mL (ng/µL)
260/280 purity ratio
1.85
Concentration (undiluted sample)
25 ng/µL
Purity check
Good for DNA (~1.8)
Conversion factors assume a 1 cm path length. Ratios depend on pH — measure in a mildly alkaline buffer (e.g. Tris) for consistent results.
What this calculator does
Converts A260 absorbance into nucleic-acid concentration and reports the 260/280 purity ratio.
What your result means
Concentration in ng/µL (equivalently µg/mL) for the measured sample after applying the dilution factor.
Formula and working
concentration = A260 × conversion factor × dilution factor (50 µg/mL dsDNA, 33 ssDNA, 40 RNA)
- 1
Collect the inputs
Nucleic acid type = 50; Absorbance at 260 nm = 0.5 A260; Absorbance at 280 nm = 0.27 A280; Dilution factor = 1 ×
- 2
Apply the formula
concentration = A260 × conversion factor × dilution factor (50 µg/mL dsDNA, 33 ssDNA, 40 RNA)
- 3
Result
Concentration = 25 µg/mL (ng/µL)
Frequently asked questions
Symbols and assumptions
- A260
- Absorbance at 260 nm
- A280
- Absorbance at 280 nm
- 260/280
- Purity ratio, ~1.8 for pure DNA and ~2.0 for pure RNA
- • A 1 cm path length or equivalent normalisation.
- • Standard conversion factors: 50 (dsDNA), 33 (ssDNA), 40 (RNA) µg/mL per absorbance unit.
Sources and review
Reviewed 2026-09-22 · Next review 2027-09-22
- • Contaminants such as phenol or guanidine distort absorbance; very low concentrations are unreliable on absorbance alone.
Important limitation
This is an educational estimate based only on the values and formula shown. Verify current rates, rules, units, and professional standards before relying on the result. It is not personalized financial or investment advice.
Report a mistake or request an improvement
Tell us if a formula, unit, explanation, or result needs attention. Your message will include this calculator’s name and page.
Related calculators
Protein Concentration (A280) Calculator
Estimate protein concentration from a 280 nm absorbance reading using the Beer–Lambert relationship.
Annealing Temperature Calculator
Estimate a PCR primer's melting temperature (Tm) and a sensible starting annealing temperature (Ta) from base composition.
Bacterial Generation Time Calculator
Work out how many generations a bacterial culture went through and its generation (doubling) time from starting and final cell counts.
Cell Dilution Calculator
Find the stock volume and diluent volume needed to reach a target cell concentration using C₁V₁ = C₂V₂.
Cell Doubling Time Calculator
Calculate the population doubling time of cultured cells from seeding and harvest counts over a known period.
Ligation Insert Amount Calculator
Calculate how much insert DNA to mix with your vector for a chosen insert:vector molar ratio.