DNA Copy Number Calculator
Calculate the number of DNA molecules in a sample from mass (ng), fragment length (bp), and strand type (single or double).
DNA Copy Number
Enter mass and length to calculate copy number
Number of DNA Molecules
Calculation Breakdown
Input mass
DNA length
Strand type
Avg. weight per bp/nt
Molecular weight of fragment
Moles in sample
Copy number
Formula Used
copies = (mass_ng × 10⁻⁹ × 6.022×10²³) / (length × bp_weight)
Copied!
Summary
Calculate the number of DNA molecules in a sample from mass (ng), fragment length (bp), and strand type (single or double).
How it works
- Enter the DNA mass in nanograms (ng) — the calculator converts to grams internally.
- Enter the fragment length in base pairs (bp); for plasmids enter the total plasmid size.
- Select ssDNA or dsDNA so the right average nucleotide weight is used (330 vs 660 g/mol).
- The tool divides total moles (mass ÷ molar mass) by Avogadro's number (6.022 × 10²³) to get molecule count.
- Read the copy number plus copies per ng for fast scaling of qPCR standard dilutions.
Use cases
- Prepare accurate molar quantities of DNA for cloning and ligation reactions.
- Determine copy number for qPCR standard curve construction.
- Calculate the number of plasmid molecules before transfection.
- Estimate template copy number for digital PCR experiments.
- Convert a sequencing library mass to molecule count for accurate pooling.
- Cross-check the IDT or Science Primer copy number calculations on your own.
Frequently Asked Questions
Last updated: 2026-06-18 ·
Reviewed by Nham Vu