SeqBench

DNA & RNA Molarity Calculator (ng ↔ pmol)

Convert between mass, moles, molarity and copy number for DNA/RNA.

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Convert nucleic-acid quantities the way you need them in the lab: ng to pmol, molar mass, molarity in nM or µM, ng/µL and copy number. Enter a length for dsDNA, ssDNA or RNA — or paste a sequence for an exact molar mass from base composition. Handy for ligation ratios, qPCR standards, library prep and normalising samples.

650,000 g/mol
Molar mass
0.15 pmol
Amount
3.1 nM
Concentration
9.26 × 10^10
Molecules
Molar mass (g/mol)650000.0
Amount of substance0.154 pmol (0.0002 nmol)
Molar concentration3.08 nM (0.0031 µM)
Mass concentration2.00 ng/µL
Copy number9.26 × 10^10

Without a sequence, molar mass uses average per-unit masses (≈650 g/mol per bp for dsDNA, 330 per nt for ssDNA, 340 per nt for ssRNA). Paste a sequence for an exact value from base composition.

Working on a whole construct rather than one calculation? Open SeqStudio — the full editor, with feature annotation, plasmid maps and GenBank export.

How to use the DNA Molarity / ng↔pmol tool

  1. 1Choose the molecule type and enter the length in bp or nt (or paste a sequence).
  2. 2Enter the mass in nanograms and, optionally, the volume in microlitres.
  3. 3Read the amount in pmol, the molar concentration and the copy number.

Frequently asked questions

How do I convert ng to pmol of DNA?

pmol = ng × 1000 / molar mass (g/mol). The molar mass comes from the length and molecule type, or exactly from a pasted sequence. Enter your mass and the tool does the conversion both ways.

What average molar masses are used?

Without a sequence we use ≈650 g/mol per base pair for dsDNA, 330 g/mol per nucleotide for ssDNA and 340 g/mol per nucleotide for ssRNA. Paste a sequence for an exact value from base composition.

How is copy number calculated?

Copies = moles × Avogadro's number (6.022 × 10²³). It is useful for making qPCR standard curves and dilution series.

More

Guides

References

DNA/RNA molecular weight

Average and exact molecular weights for DNA and RNA sequences.

Oligo & DNA/RNA conversions

A260 quantification, ng↔pmol, copy number and oligo resuspension.

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