DNA Concentration Calculator

Quantify your nucleic acids. Enter your spectrophotometer readings to determine the concentration of dsDNA, ssDNA, or RNA in your sample.

Absorbance at 260nm (A260)*

Nucleic Acid Type

Dilution Factor

Concentration (µg/mL) = A260 × Conversion Constant × Dilution Factor Constants (at A260): • dsDNA: 50 µg/mL per 1.0 A unit • ssDNA: 33 µg/mL per 1.0 A unit • RNA: 40 µg/mL per 1.0 A unit

Scenario: You measure a sample of double-stranded DNA (dsDNA) in a spectrophotometer. The absorbance reading at 260nm is 0.450 (A260). The sample was diluted 1:50 before measurement. Calculation: 1. Absorbance (A260) = 0.450. 2. Constant (dsDNA) = 50. 3. Dilution Factor = 50. 4. Concentration = 0.450 × 50 × 50 = 1,125 µg/mL. Result: The original stock concentration is 1,125 µg/mL (or 1.125 mg/mL).

How is DNA concentration calculated from absorbance?

DNA concentration is determined using UV spectrophotometry. The standard constant for double-stranded DNA (dsDNA) is 50 µg/mL per A260 unit. Formula: Concentration = A260 × Dilution Factor × Constant.

What constants are used for other nucleic acids?

Standard constants at A260 are: dsDNA = 50 µg/mL, ssDNA = 33 µg/mL, and RNA = 40 µg/mL.

What is the A260/A280 ratio?

This ratio is used to assess nucleic acid purity. A ratio of ~1.8 is generally accepted as "pure" for DNA, while ~2.0 is accepted for RNA. Lower ratios may indicate protein or phenol contamination.

Why do I need a dilution factor?

If your sample was diluted before being measured in the spectrophotometer, you must multiply the result by the dilution factor to find the original concentration.

🔗 Related Calculators

📐 Formula

Concentration (µg/mL) = A260 × Conversion Constant × Dilution Factor Constants (at A260): • dsDNA: 50 µg/mL per 1.0 A unit • ssDNA: 33 µg/mL per 1.0 A unit • RNA: 40 µg/mL per 1.0 A unit

📝 Example Calculation

❓ Frequently Asked Questions

How is DNA concentration calculated from absorbance?▼

What constants are used for other nucleic acids?▼

Standard constants at A260 are: dsDNA = 50 µg/mL, ssDNA = 33 µg/mL, and RNA = 40 µg/mL.

What is the A260/A280 ratio?▼

This ratio is used to assess nucleic acid purity. A ratio of ~1.8 is generally accepted as "pure" for DNA, while ~2.0 is accepted for RNA. Lower ratios may indicate protein or phenol contamination.

Why do I need a dilution factor?▼

If your sample was diluted before being measured in the spectrophotometer, you must multiply the result by the dilution factor to find the original concentration.