DNA Concentration Calculator
Calculate DNA, RNA, and oligonucleotide concentrations from UV absorbance measurements at 260nm
Calculate Nucleic Acid Concentration
Conversion factors: dsDNA = 50 μg/mL, ssDNA = 33 μg/mL, RNA = 40 μg/mL
UV absorbance reading from spectrophotometer
Standard cuvette pathlength is 1 cm
Use 1 for undiluted samples
For 260/280 ratio purity assessment
Concentration Results
Formula used: C = (A₂₆₀ / pathlength) × conversion factor × dilution factor
Pathlength: 1.00 cm (1 cm)
Conversion factor: 50 μg/mL for dsDNA
Good concentration range: 10-300 ng/μL for most applications
DNA Yield Calculation
Example Calculations
Genomic DNA Extraction Example
Sample: Double-stranded genomic DNA
Absorbance at 260nm (A₂₆₀): 0.75
Absorbance at 280nm (A₂₈₀): 0.42
Pathlength: 1 cm (standard cuvette)
Dilution factor: 1 (undiluted)
Calculation
Concentration = (A₂₆₀ / pathlength) × CF × DF
Concentration = (0.75 / 1) × 50 × 1
Concentration = 37.5 μg/mL
260/280 ratio = 0.75 / 0.42 = 1.79 (Pure DNA)
Oligonucleotide Example
Sequence: AGGTC (5-mer ssDNA oligo)
Molecular Weight: 1,503 g/mol
Extinction Coefficient: 49,300 M⁻¹cm⁻¹
A₂₆₀: 0.49, Pathlength: 1 cm, DF: 1
C = (A₂₆₀ × MW × DF) / (ε₂₆₀ × l)
C = (0.49 × 1,503 × 1) / (49,300 × 1)
C = 14.9 μg/mL
Purity Standards
260/280 Ratio
~1.8 for pure DNA
<1.7 indicates protein contamination
260/280 Ratio
~2.0 for pure RNA
<1.8 indicates protein contamination
260/230 Ratio
2.0-2.2 for pure samples
<2.0 indicates salt/organic contamination
Measurement Tips
Use UV-transparent cuvettes (quartz or UV plastic)
Blank with the same buffer used for dilution
Optimal absorbance range: 0.1-1.0 at 260nm
Dilute samples if A₂₆₀ > 1.0 for accuracy
Check for air bubbles in cuvette
Understanding DNA Concentration Measurement
Spectrophotometric Analysis
DNA and RNA quantification using UV spectrophotometry is based on the absorption of ultraviolet light by nucleic acid bases. The maximum absorption occurs at 260nm, making it ideal for concentration measurements.
Why 260nm?
- •Aromatic bases (A, T, G, C, U) absorb UV light maximally at 260nm
- •Provides specific detection of nucleic acids
- •Minimal interference from proteins (which absorb at 280nm)
- •Reproducible and quantitative measurements
Beer-Lambert Law
C = (A₂₆₀ / l) × CF × DF
C: Concentration (μg/mL)
A₂₆₀: Absorbance at 260nm
l: Pathlength (cm)
CF: Conversion factor
DF: Dilution factor
Conversion Factors
dsDNA: 50 μg/mL (double helix structure)
ssDNA: 33 μg/mL (single strand)
RNA: 40 μg/mL (ribose sugar backbone)
Oligonucleotides: Custom calculation using molecular weight and extinction coefficient
Oligonucleotide Formula
C = (A₂₆₀ × MW × DF) / (ε₂₆₀ × l)
MW: Molecular weight (g/mol)
ε₂₆₀: Extinction coefficient (M⁻¹cm⁻¹)
Result: Concentration in μg/mL