Enter measurement details
Formula used
The calculator estimates RNA concentration from UV absorbance at 260 nm, corrected to a 1 cm path length.
- A260(1cm) = A260 / path_length_cm
- RNA (ng/µL) = A260(1cm) × factor × dilution_factor
- RNA (µg/mL) = RNA (ng/µL) (numerically equal)
- A260/A280 = A260 ÷ A280 (if A280 provided)
- A260/A230 = A260 ÷ A230 (if A230 provided)
Commonly used factor for RNA is 40 ng/µL per A260 at 1 cm path length.
How to use this calculator
- Measure your sample absorbance at 260 nm.
- Optionally record absorbance at 280 nm and 230 nm.
- Enter dilution factor used before reading the sample.
- Enter the path length in centimeters for your measurement.
- Keep factor at 40 for RNA unless you need a custom value.
- Press Calculate to view concentration and purity ratios.
- Use CSV or PDF export for documentation and sharing.
Example data table
| Sample | A260 | A280 | A230 | Dilution | Path (cm) | Factor | RNA (ng/µL) | A260/A280 | A260/A230 |
|---|---|---|---|---|---|---|---|---|---|
| RNA-01 | 0.325 | 0.165 | 0.150 | 10 | 1.00 | 40 | 130.0 | 1.97 | 2.17 |
| RNA-02 | 0.120 | 0.070 | 0.090 | 1 | 0.20 | 40 | 24.0 | 1.71 | 1.33 |
| RNA-03 | 0.540 | 0.260 | 0.240 | 5 | 1.00 | 40 | 108.0 | 2.08 | 2.25 |
Values are illustrative and may not match your instrument setup.
FAQs
1) What does A260 measure for RNA?
A260 reflects nucleic acid absorbance at 260 nm. For RNA, it is commonly used to estimate concentration when combined with a conversion factor and dilution information.
2) Why is the factor set to 40?
A widely used convention is 1.0 absorbance unit at 260 nm equals 40 µg/mL for RNA at 1 cm path length. Your kit or instrument may define a different factor.
3) What is the purpose of path length?
Absorbance scales with optical path length. If you measure with a path length other than 1 cm, the calculator normalizes A260 to a 1 cm equivalent before computing concentration.
4) What A260/A280 ratio is considered good for RNA?
Many labs expect RNA around ~2.0, often within roughly 1.9–2.1. Lower values can suggest protein or phenol carryover, but context and instrument settings matter.
5) What does a low A260/A230 indicate?
Low A260/A230 may suggest contamination from salts, guanidine, phenolics, or carbohydrates. It can also reflect poor blanking or leftover extraction reagents.
6) Can I use this for DNA instead of RNA?
You can, but you should change the conversion factor to match DNA conventions. Many protocols use 50 µg/mL per A260 for double-stranded DNA at 1 cm.
7) Why do my ratios look unusual even with clean RNA?
Baseline subtraction, dirty blanks, bubbles, low concentration noise, or instrument path length estimates can distort ratios. Reblank, remeasure, and confirm with an alternative quantification method if needed.