DNA Copy Number Calculator
Determine the number of template molecules present in a given mass of double-stranded DNA. Useful for setting up qPCR standard curves.
DNA Parameters
Input the DNA quantity and sequence length.
Copy Number
Expert Tip
For single-stranded DNA templates (such as viral RNA or ssDNA primers), replace the average bp weight in your manual calculation with approximately 330 g/mol per nucleotide instead of 660.
Methodology & Equations
DNA Copy Number Equation
The mathematical formula used to calculate the number of double-stranded DNA template copies is:
Constant Values Explanation
- Avogadro's constant: 6.022 × 1023 molecules/mole.
- Conversion factor: 10-9 g/ng to convert nanograms to grams.
- Average molecular weight of a bp: 660 grams/mole.
How to Calculate DNA Copy Number: Step-by-Step
Below is a step-by-step walkthrough of calculating copy number for 1 ng of a 3,000 bp plasmid:
Convert Mass to Grams
Convert the mass of DNA from nanograms to grams by multiplying by 10-9.
Example: 1 ng × 10-9 g/ng = 1.0 × 10-9 grams.
Calculate Molecular Weight of the Template
Multiply the sequence length by the average double-stranded nucleotide weight (660 g/mol/bp).
Example: 3,000 bp × 660 g/mol/bp = 1,980,000 g/mol.
Calculate Copy Count
Divide the DNA mass in grams by the template molecular weight to get moles, then multiply by Avogadro's number.
Formula: Copies = (1 × 10-9 g / 1,980,000 g/mol) × (6.022 × 1023 molecules/mol)
Result: 3.04 × 108 molecules.
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