Molarity to copy number
Convert a molar concentration (nM) and a sample volume into the number of molecules (copies), using Avogadro’s number.
How it works
Formula
molecules = concentration (mol/L) × volume (L) × 6.02214076×10²³. A nM is 10⁻⁹ mol/L and a µL is 10⁻⁶ L.
Worked example
1 nM in 1 µL = (1×10⁻⁹ mol/L) × (1×10⁻⁶ L) × 6.02214076×10²³ ≈ 6.02×10⁸ molecules.
When to use it
To check the absolute number of template molecules going into a reaction — for example confirming enough copies for low-input library prep, ddPCR, or input to an amplification.
Sensible defaults
Defaults compute the copies in 1 µL of a 1 nM solution (≈ 6.02×10⁸ molecules).
FAQ
- Does this depend on fragment length?
- No. Copy number from molarity is purely molarity × volume × Avogadro. Length only matters if you start from a mass concentration — convert with the ng/µL ⇄ nM tool first.
- What is Avogadro’s number?
- 6.02214076×10²³, the number of entities in one mole — here, the number of molecules per mole of DNA.