DNA Copy Number Calculator (ng to Copies)
Enter the DNA mass and length to get the number of copies.
Your numbers
Your results
Number of copies
Number of copies
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Molecular weight (g/mol)
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Amount in picomoles
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Copies per µL if diluted in 1 µL
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DNA Copy Number Calculator (ng to Copies) by TheCalcTools
How the DNA Copy Number Calculator (ng to Copies) works
Divide the mass by the molecular weight to get moles, then multiply by Avogadro’s number. An average base pair of double-stranded DNA weighs about 650 g/mol (617.96 plus small corrections for ends and counter-ions).
The formula
Copies = mass (g) ÷ (length × 650 g/mol) × 6.022 × 10²³
Worked example
Using the default values shown in the calculator:
| Amount of DNA (ng) | 10 |
|---|---|
| Length (base pairs) | 5000 |
| Molecule | Double-stranded DNA (650 g/mol per bp) |
- 10 ng of a 5,000 bp plasmid: 10 × 10⁻⁹ ÷ (5,000 × 650) × 6.022 × 10²³ = 1853000000 copies.
Result:
| Number of copies | 1853000000 |
|---|---|
| Molecular weight (g/mol) | 3,250,000 |
| Amount in picomoles | 0.0031 |
| Copies per µL if diluted in 1 µL | 1853000000 |
Frequently asked questions
Why do some calculators use 660 g/mol?
It is another common average, including the sodium salt. The difference is about 1.5%.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.