How to use this calculator
- Enter the blank-corrected A260 reading.
- Enter the total dilution factor used before reading.
- Confirm the conversion factor for your RNA method.
- Select Calculate and use the original-sample result for planning.
#3271 · Science & Engineering Tool
RNA Concentration Calculator
Convert a blank-corrected A260 reading into RNA concentration while accounting for sample dilution and the selected absorbance conversion factor. The result reports the original-sample concentration, the concentration in the measured dilution, and an equivalent ng/µL value so you can plan normalization, storage, or downstream reactions without mixing units.
Calculator
Laboratory inputsFormula
Original concentration (µg/mL) = A260 × conversion factor × dilution factor
The measured-dilution concentration omits the dilution factor. Because 1 µg/mL equals 1 ng/µL, those displayed values are numerically equal.
What the result means
The main result estimates RNA concentration in the undiluted source sample. It depends directly on accurate blanking, dilution preparation, and the conversion factor appropriate to the nucleic acid.
This absorbance estimate does not correct for contaminants or distinguish intact RNA from degraded RNA. Review spectral purity and assay requirements separately.
Example calculation
For A260 = 0.25, a 20× dilution, and a 40 µg/mL conversion factor: 0.25 × 20 × 40 = 200 µg/mL, equivalent to 200 ng/µL. The measured dilution contains 10 µg/mL.
Tips for better results
- Use the same buffer for the sample and blank.
- Record every dilution step in the total factor.
- Re-read samples outside the instrument's linear range.
- Use a fluorescence assay when sequence-specific sensitivity matters.
- Keep units consistent when setting reaction inputs.
Frequently asked questions
Why is 40 used as the RNA A260 conversion factor?
A factor of 40 µg/mL per A260 is a conventional estimate for single-stranded RNA; use a method-specific factor when your protocol specifies one.
Should the dilution factor include every dilution step?
Yes. Multiply sequential dilution factors and enter the combined value.
Is µg/mL numerically equal to ng/µL?
Yes. Both units represent the same mass concentration and therefore have the same numeric value.
Can an A260 reading confirm RNA purity?
No. Concentration alone does not establish purity; review additional absorbance ratios or an appropriate quality assay.
What should I enter for an undiluted RNA sample?
Enter a dilution factor of 1.
Related calculators
RNA concentration variables
| Variable | Unit | Role |
|---|---|---|
| A260 | absorbance | Blank-corrected reading |
| Dilution factor | × | Restores original concentration |
| Conversion factor | µg/mL per A260 | Converts absorbance to RNA mass concentration |