dsDNA mass & molarity
ng ↔ pmol, ng/µL ↔ nM, copy number, mass ↔ volume.
What this calculator does
Convert double-stranded DNA between ng and pmol, ng/µL and nM, copy number and volume, using the average 650 g/mol per base pair model.
Calculation model
Average-mass dsDNA model (650 g/mol/bp)
Formulas
- F07 · dsDNA mass ↔ amount:
n_pmol = 1000 · m_ng / (650 · L_bp);m_ng = n_pmol · 650 · L_bp / 1000 - F08 · dsDNA concentration ↔ molarity:
C_nM = 10⁶ · C_ng/µL / (650 · L_bp);C_ng/µL = C_nM · 650 · L_bp / 10⁶ - F09 · DNA molecule count:
copies = (m_ng · 10⁻⁹ / (650 · L_bp)) · N_A;N_A = 6.02214076 × 10²³ mol⁻¹ - F10 · DNA mass ↔ volume:
m_ng = C_ng/µL · V_µL;V_µL = m_ng / C_ng/µL
Assumptions
- dsDNA average molar mass 650 g/mol per bp (NEB convention, [S02]); an approximation. Tools using 660 g/mol/bp give ~1.5 % different results.
- Double-stranded DNA only; not valid for ssDNA, oligos or RNA.
- Length is an integer number of base pairs; topology (linear/circular) does not change mass.
Verification status
- Measured concentration accuracy (A260, fluorometry) usually dominates the error of these conversions.
- tests-passed means automated algorithm tests (unit, property, integration and browser end-to-end) pass. It is not an independent scientific review and not laboratory validation.
References
- [S02] NEB: NEBuilder HiFi DNA Assembly reaction protocol / instruction manual (650 g/mol/bp approximation) (accessed 2026-10-29)
- [S01] NEB: NEBioCalculator (DNA, ligation, OD260, dilution and molarity calculators) (accessed 2026-10-29)
The calculator runs in your browser and needs JavaScript. Your inputs are processed locally.