Biology & Life Science

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DNA Copy Number Calculator.

Estimate dsDNA molecule copies from mass and base-pair length.

On-device calculationNo signup
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Set your values

Results update as you type.

Molecular weight: 660,000 g/mol

Molecular weight

660,000.000000g/mol
DNA copies: 912,445,569.69697 copies

DNA copies

912,445,569.696970copies

Educational arithmetic only. Enter measured values and keep units consistent. No crop, feed, veterinary, or experimental recommendation is inferred.

Use Cases

Quantify DNA for PCR or sequencing

Determine the number of template molecules in a sample to optimize PCR reactions or ensure adequate coverage for sequencing.

Example: If you have 10 ng of a 500 bp PCR product, the calculator tells you how many copies you have.

Prepare standard curves for qPCR

Create serial dilutions of a known DNA standard to generate a standard curve for absolute quantification.

Example: Calculate copy numbers for a plasmid standard of 3000 bp to set up a standard curve.

Frequently Asked Questions

How does the DNA copy number calculator work?
This calculator estimates the number of dsDNA molecules by using the mass (in ng) and the length (in bp). It uses Avogadro's number and the average molecular weight of a base pair to convert mass to copy number.
What units are required for the DNA mass and length?
The DNA mass must be entered in nanograms (ng), and the DNA length must be entered in base pairs (bp). The calculator uses these units to compute the copy number.
Is this calculator suitable for single-stranded DNA?
No, this calculator is specifically designed for double-stranded DNA (dsDNA). For single-stranded DNA, the calculation would differ because the molecular weight per base is different.

Tips & Common Mistakes

Tips

  • Ensure the DNA mass is measured accurately, as small errors can significantly affect the copy number estimate.
  • Use the average molecular weight of a base pair (660 Da) for dsDNA, which is standard for this calculation.
  • For circular DNA like plasmids, the length in bp should include the entire plasmid sequence.
  • Double-check that the mass is in nanograms (ng) and length in base pairs (bp) before calculating.

Common Mistakes to Avoid

  • Using the mass in micrograms (µg) instead of nanograms (ng) without converting, leading to a 1000-fold error.
  • Entering the length in kilobases (kb) instead of base pairs (bp), which would underestimate the copy number.
  • Assuming the calculator works for single-stranded DNA or RNA, which have different molecular weights.

Last updated: August 13, 2026