Convert between mass, moles, and copies for dsDNA, ssDNA, ssRNA, and dsRNA. OD₂₆₀ concentration, ligation insert mass, C₁V₁ = C₂V₂ dilution, and qPCR copy-number calculations — all in one tabbed tool. Runs entirely in your browser.
Try it out
Load example bio converter data to see the full workflow
Don't use for
The molecular weight of a nucleic acid depends on its length and type. For dsDNA, the average MW per base pair is ~649 Da (counting both strands and the Na⁺ counterion). For ssDNA it is ~330 Da per nucleotide, for ssRNA ~340 Da/nt, and for dsRNA ~680 Da/bp.
To convert between mass and moles:
So 1 ng of a 1,000 bp dsDNA fragment (MW = 649,000 Da) contains about 1.54 fmol or ~9.3 copies.
Nucleic acids absorb UV light at 260 nm due to purine and pyrimidine ring systems. The Beer–Lambert law relates absorbance to concentration: , where is the extinction coefficient, c is concentration, and l is the path length.
The standard convention: 1 OD₂₆₀ unit = 50 ng/µL for dsDNA, 33 ng/µL for ssDNA, 40 ng/µL for ssRNA. These are approximations for "average" base composition. For precise work on known sequences, use the exact extinction coefficient computed from the nucleotide sequence.
For sticky-end ligations, a 1:3 vector:insert molar ratio is the standard starting point. For blunt-end ligations, try 1:5 or 1:10 because blunt-end ligation is less efficient.
The formula insert_ng = (insert_size / vector_size) ratio vector_ng ensures you add the right molar ratio regardless of fragment sizes. If your insert is half the size of your vector, you need half the mass for a 1:1 molar ratio.
