660,000
Da
660
kDa
0.66
MDa
1.5152
pmol
0.66
µg
660,000
Da
660
kDa
0.66
MDa
1.5152
pmol
0.66
µg
The DNA Molecular Weight Calculator estimates the molecular weight of a DNA molecule based on its length and strand type. Knowing the molecular weight is essential for converting between mass and molar quantities, preparing gel electrophoresis size standards, and performing stoichiometric calculations in cloning and ligation reactions. This tool supports both double-stranded (dsDNA) and single-stranded (ssDNA) calculations.
The molecular weight is calculated using the average mass per base pair or nucleotide:
For dsDNA: MW = Length (bp) × 660 Da/bp
For ssDNA: MW = Length (nt) × 330 Da/nt
Where:
These values are averages across all four nucleotides. The actual molecular weight varies slightly depending on the base composition (GC vs AT content).
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Results
A 1000 bp double-stranded DNA fragment has a molecular weight of 660,000 Da (660 kDa).
Inputs
Results
A 25-nucleotide single-stranded DNA oligonucleotide has a molecular weight of approximately 8,250 Da (8.25 kDa).
The four deoxyribonucleotides have individual molecular weights ranging from ~313 Da (dCMP) to ~351 Da (dGMP). The average nucleotide is approximately 330 Da. Since dsDNA has two strands, you multiply by 2 to get ~660 Da per base pair. This figure includes the sodium counterion typically present under physiological conditions.
Use exact calculations when working with short oligonucleotides (<50 nt) for mass spectrometry, when the sequence has unusual modifications (e.g., phosphorothioate backbones, fluorescent labels), or when high precision is required for stoichiometric calculations. For routine cloning and gel electrophoresis work, the average estimate is perfectly adequate.
Use the formula: moles = mass (g) / MW (g/mol). For practical lab quantities: pmol = µg / (MW × 10⁻⁶). For example, 1 µg of a 660,000 Da plasmid is: 1 / (660000 × 10⁻⁶) = 1.52 pmol.
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