DNA Concentration Calculator

Summary

This calculator applies the Beer-Lambert law (A = ε × c × l) to convert UV absorbance at 260 nm into nucleic acid concentration. Standard extinction coefficients are used: 50 ng/µL per A260 unit for double-stranded DNA, 33 ng/µL for single-stranded DNA, and 40 ng/µL for RNA. Enter your spectrophotometer reading and path length to get an instant concentration result.

How it works

1. Select the nucleic acid type: dsDNA, ssDNA, or RNA.
2. Enter the A260 absorbance value from your spectrophotometer.
3. Optionally enter the A280 reading to calculate the A260/A280 purity ratio.
4. Set the path length (default 1 cm; standard cuvettes and normalized NanoDrop readings use 1 cm).
5. The calculator applies Beer-Lambert law with the appropriate extinction coefficient.
6. Results show concentration in ng/µL, µg/mL, and µg/µL, plus a purity assessment.

Use cases

• Quantify genomic DNA after extraction before PCR or sequencing.
• Measure RNA concentration after isolation for transcriptomics experiments.
• Assess purity of nucleic acid samples using the A260/A280 ratio.
• Calculate the amount of ssDNA oligonucleotide in a synthetic primer stock.
• Determine concentration from a NanoDrop or cuvette spectrophotometer reading.
• Verify DNA yield after gel purification or column cleanup.
• Prepare dilutions for library preparation at a known concentration.
• Cross-check fluorometric (PicoGreen) vs. UV absorbance measurements.

Frequently Asked Questions