Worked example
A 5,000 bp dsDNA molecule at 5 ng/µL has an estimated molecular weight of 3.30 × 106 g/mol, 1.52 fmol/µL, and approximately 9.12 × 108 copies/µL.
DNA & RNA
DNA & RNA Copy Number Calculator
Estimate molecular weight, fmol/µL, copies per volume, total copies, and an optional target-copy dilution using an explicit molecular-weight assumption.
Calculations run locally in your browser. Values are only placed in a URL when you choose “Copy Shareable Link.”
How to use
- Select the molecule type and enter length or use a pasted sequence to populate it.
- Enter mass concentration and optional sample volume.
- Review both molar concentration in fmol/µL and molecular copies per volume.
- Optionally calculate a dilution to a target copies-per-volume value.
Assumptions
dsDNA uses 660 g/mol per bp; ssDNA uses length × 307.97 + 18.02 g/mol; the ssRNA transcript mode uses length × 320.5 + 159 g/mol and explicitly assumes a 5′ triphosphate. Femtomoles and copies use the same selected molecular-weight source as the Mass ↔ Moles Calculator. Modified nucleic acids require custom molecular weight.
Validation and limitations
This is a molecular-count estimate based on the selected molecular-weight assumption. It does not account for sample purity, fragmentation, damaged molecules, incomplete genomes, or amplifiability. Calculated molecular copies are not equivalent to amplifiable copies unless the assay and sample support that assumption. This is not a diagnostic or clinical calculator.
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