Calculadora de Concentração de DNA
- Created by
- Renato Passos, Eng. de Software
- Reviewed by
- Renato Passos, Eng. de Software
Last updated: Apr 18, 2026
Formula
C (ng/μL) = A260 × fator × diluição
About this calculator
The DNA Concentration Calculator estimates the concentration of nucleic acids in a sample based on absorbance measured at 260 nm (A260). The principle follows the Beer-Lambert law, where absorbance is proportional to concentration. For double-stranded DNA (dsDNA), a factor of 50 ng/μL per A260 unit is used; for single-stranded DNA (ssDNA), the factor is 33 ng/μL; and for RNA, the factor is 40 ng/μL. The formula also incorporates the dilution factor if the sample was diluted before measurement.
This tool is widely used in molecular biology laboratories, for example, to quantify plasmid DNA, PCR products, or extracted RNA. The typical procedure involves measuring absorbance in a spectrophotometer (such as NanoDrop), entering the A260 value, selecting the nucleic acid type, and entering the dilution factor. The result is given in ng/μL, facilitating experiment planning such as cloning, sequencing, or enzymatic reactions.
Important considerations: absorbance at 260 nm can be affected by contaminants like proteins (absorb at 280 nm) or phenolic compounds. It is recommended to check sample purity using the A260/A280 ratio (ideal ~1.8 for dsDNA, ~2.0 for RNA). Additionally, the reading should be within the spectrophotometer's linear range (typically A260 between 0.1 and 1.0) to ensure accuracy. Highly concentrated samples should be diluted appropriately.
Frequently asked questions
What is the difference between the factors for dsDNA, ssDNA, and RNA?
The factors reflect specific absorbance: dsDNA has factor 50, ssDNA 33, and RNA 40. This is because double-stranded structure absorbs less light per mass unit than single-stranded, and RNA has a different base composition.
Do I need to dilute my sample before measuring?
Yes, if the expected absorbance is above 1.0, dilute to fall between 0.1 and 1.0. Enter the dilution factor in the calculator to obtain the original concentration.
What does the A260/A280 ratio mean?
It indicates sample purity. For dsDNA, values around 1.8 are considered pure; for RNA, ~2.0. Low values suggest contamination by proteins or phenol.
Can I use this calculator for messenger RNA?
Yes, select the RNA option. Remember that RNA is more prone to degradation; keep samples on ice and use RNase-free equipment.
Does the calculator account for background absorbance?
No. It is recommended to measure absorbance at 320 nm to correct for turbidity, but the calculator assumes the A260 value is already corrected.