CALCULATE WITH CONFIDENCE

PCR, qPCR & Molecular Biology

DNA Mass-to-Molecule and Copy Number Workbench

Convert a declared total DNA mass or mass concentration into moles and molecules using an explicit approximate dsDNA, approximate ssDNA or exact entered molecular-mass basis.

Biology · experimental measurements

Keep mass, length, molecular-mass convention, Avogadro conversion and optional volume normalization visible instead of presenting copy number as a property of mass alone.

Private calculations in your browser · explicit inputs and model boundaries
Example preview · Plasmid massMolecule count scales linearly with entered mass
002.62e81.255.23e82.57.85e83.751.05e95Total mass (ng)Calculated molecules

The line holds the declared molecular-mass basis constant and scales from zero to the entered total mass.

  1. 1EnterProvide the known values
  2. 2CalculateResults update automatically
  3. 3VerifyReview the details and units
Try an example

Enter values in bp or nt.

Calculation result

—

Enter valid values to see the result.

Your entries are calculated in this browser and are not submitted to 365CALCS.COM.

Feedback

Understand the relationship

The reasoning behind the result

Mass needs a molecular denominator

n = m/M

Moles divide entered grams by grams per mole.

Length-average 660 and 330 values are approximations, not exact sequence chemistry.

Avogadro conversion counts molecules

molecules = n × 6.02214076×10²³

The result is a mathematical molecule count for the entered mass basis.

It does not establish intact, amplifiable or biologically active copies.

Volume changes concentration, not total count

A mass concentration must be multiplied by its sample volume before total molecules are calculated.

Copies per reaction require a separately declared transferred volume and recovery model.

Follow the numbers

Convert a declared plasmid mass

  1. Convert 5 ng to 5×10⁻⁹ g.
  2. Approximate molecular mass as 4,361×660 g/mol.
  3. Divide mass by molecular mass.
  4. Multiply moles by the Avogadro constant.

The result is a molecule count under the declared average dsDNA mass model.

Quick guide

How to use this calculator

  1. Choose whether the entered mass is a total or a concentration that must be multiplied by sample volume.
  2. Declare an approximate length basis or enter an independently established exact molecular mass.
  3. Keep measured purity, recovery, target copies per molecule and assay-accessible copies separate from molecule count.

Calculation method

Calculation and interpretation

Keep mass, length, molecular-mass convention, Avogadro conversion and optional volume normalization visible instead of presenting copy number as a property of mass alone.

Moles = mass(g)/molecular mass(g·mol⁻¹); molecules = moles×NA. Approximate molecular mass = length×660 for dsDNA or length×330 for ssDNA.

Worked example

Convert a declared plasmid mass

The result is a molecule count under the declared average dsDNA mass model.

Moles = mass(g)/molecular mass(g·mol⁻¹); molecules = moles×NA. Approximate molecular mass = length×660 for dsDNA or length×330 for ssDNA.

Supported inputs

Precision and limits

Mass model is explicit

The 660 g/mol/bp and 330 g/mol/nt options are average approximations; exact sequence, ends and modifications can differ.

Molecules are not target copies

Targets per molecule, genome ploidy, concatemerization and fragment integrity are not inferred.

No recovery correction

Purity, extraction yield, adsorption, degradation and pipetting loss remain external.

No assay accessibility

The result does not establish amplifiable, ligatable, transfectable or viable copies.

Continue calculating

Related calculators