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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.”

Molecule and sample

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.

How to use

  1. Select the molecule type and enter length or use a pasted sequence to populate it.
  2. Enter mass concentration and optional sample volume.
  3. Review both molar concentration in fmol/µL and molecular copies per volume.
  4. 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.

Calculation record

Methodology and scientific authority

Estimate molecular weight, molar concentration, copies per volume, total copies, and a target-copy dilution.

Engine
nucleic-acid-copy-number 1.1.0
Content updated

Methodology

Converts mass concentration to moles using the selected molecular-weight model, then multiplies by the exact Avogadro constant for molecular copies.

Inputs

  • molecule type
  • length or custom molecular weight
  • mass concentration
  • optional sample volume and target

Outputs

  • molecular weight
  • fmol per µL
  • copies per µL and mL
  • total copies
  • target dilution

Validation examples

These scientific fixtures are reproducible tests of the calculation engine, not build-only checks.

  • 1,000 bp dsDNA at 1 ng/µL yields about 9.124 × 10^8 copies/µL. Test: one-kb-copy-number
  • Avogadro and default molecular-weight constants are locked by regression tests. Test: constant-drift

Assumptions and limitations

Assumptions

  • dsDNA uses 660 g/mol per bp; ssDNA and ssRNA use the explicitly stated average models.
  • Custom molecular weight is required for modified nucleic acids.

Limitations

  • Estimated molecular copies do not establish purity, integrity, amplifiability, infectivity, or biological activity.
  • Sequence input supplies length only; it is not used for exact composition-dependent molecular weight.

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