DNA Molecular Weight Calculator
FREE TOOL
0 valid bases
Accepts .txt, .fasta, .fa files — FASTA headers removed automatically
0
g/mol (Daltons)
0 kDa
Kilodaltons
0 bp
Sequence Length
dsDNA
Strand Type
Nucleotide Contribution Breakdown
How to Use the DNA Molecular Weight Calculator
Step 1: Enter your DNA sequence in the input box above.
Step 2: Select whether your sequence is single stranded or double stranded.
Step 3: Select the end type — most laboratory DNA has a 5' phosphate group by default.
Step 4: Click Calculate MW. The result shows molecular weight in g/mol, kDa, and a breakdown by nucleotide contribution.
How DNA Molecular Weight is Calculated
The molecular weight of a DNA sequence is calculated by summing the molecular weights of all individual nucleotides and subtracting water molecules lost during phosphodiester bond formation.
// Monoisotopic MW of DNA nucleotides (5' phosphate):
dAMP (Adenine) = 331.22 g/mol
dTMP (Thymine) = 322.21 g/mol
dGMP (Guanine) = 347.22 g/mol
dCMP (Cytosine) = 307.20 g/mol
// Formula for ssDNA:
MW = (nA × 331.22) + (nT × 322.21) +
(nG × 347.22) + (nC × 307.20) - 61.96
// For dsDNA — add complement strand MW
dAMP (Adenine) = 331.22 g/mol
dTMP (Thymine) = 322.21 g/mol
dGMP (Guanine) = 347.22 g/mol
dCMP (Cytosine) = 307.20 g/mol
// Formula for ssDNA:
MW = (nA × 331.22) + (nT × 322.21) +
(nG × 347.22) + (nC × 307.20) - 61.96
// For dsDNA — add complement strand MW
Reference Molecular Weights
| Nucleotide | Base | MW (5' Phosphate) g/mol | MW (5' OH) g/mol |
|---|---|---|---|
| dAMP | Adenine | 331.22 | 251.24 |
| dTMP | Thymine | 322.21 | 242.23 |
| dGMP | Guanine | 347.22 | 267.24 |
| dCMP | Cytosine | 307.20 | 227.22 |