MAXScanner biology & lab calculator
DNA Copy Number Calculator — ng/µL, bp, Copies/µL & qPCR Copies
Convert dsDNA or ssDNA mass concentration and fragment length into molecules per microlitre, total molecules and qPCR template copies per reaction. Optional exact molecular weight overrides the base-pair estimate.
Results
Formula, example and assumptions
MW≈length×660 g/mol for dsDNA or ×330 g/mol for ssDNA; copies/µL=(ng/µL×10⁻⁹/MW)×Nₐ; copies/reaction=copies/µL×template µL.
A 150 bp dsDNA amplicon at 10 ng/µL contains about 6.08×10¹⁰ molecules/µL; adding 2 µL contributes about 1.22×10¹¹ template molecules.
- 660 and 330 g/mol per base are average planning approximations; use an exact vendor molecular weight when available.
- Copy number is a molecule-count conversion, not a prediction of qPCR amplification efficiency or measured Ct/Cq.
Frequently asked questions
Does circular plasmid DNA use a different molecular weight formula?
Topology does not materially change the base-pair mass conversion. Use the full plasmid length and dsDNA molecular weight unless you have an exact molecular weight.
How do I get copies per qPCR reaction?
Calculate copies per microlitre from concentration and fragment length, then multiply by the template volume added to one reaction.