OD260/280 Concentration
Calculate DNA/RNA concentration from OD260/280 absorbance
Extinction factor: 50 µg/mL per OD | Ideal 260/280: 1.8–2
Tool Guide
Definition
OD260/280 concentration calculator — Calculate nucleic acid concentration (µg/mL, ng/µL) from 260 nm absorbance, dilution factor, and nucleic-acid-specific extinction factor (NanoDrop, etc.). Also evaluates protein contamination via A260/A280 ratio.
Purpose
(1) Measure genomic DNA / plasmid prep concentration (e.g., NanoDrop 1 µL) (2) RNA prep concentration + purity check (A260/A280 ≥ 1.8, A260/A230 ≥ 2.0 recommended) (3) Verify ssDNA oligo / primer concentration (4) Compute input mass for PCR/cloning (ng/µL → ligation amounts)
How to Use
① Choose sample type (dsDNA: 50 µg/mL per OD / ssDNA: 33 / RNA: 40 / ssOligo: 33) ② Enter A260 reading ③ Dilution factor (NanoDrop usually 1; cuvette with 100× dilution = 100) ④ Path length (NanoDrop 1 mm = 0.1 cm, cuvette 1 cm) ⑤ Optional A280 → auto-computes A260/A280 ratio Output: Concentration (ng/µL), A260/A280 ratio + purity comment.
Examples
Example 1) Plasmid prep (dsDNA), NanoDrop → A260 = 0.45, A280 = 0.24, dilution = 1, path = 1 cm → Conc = 0.45 × 50 × 1 = 22.5 µg/mL = 22.5 ng/µL → A260/A280 = 1.88 → good Example 2) Total RNA TRIzol extraction → A260 = 1.20, A280 = 0.60, dilution = 100 → Conc = 1.20 × 40 × 100 = 4,800 µg/mL = 4.8 µg/µL → A260/A280 = 2.0 → good