What molecular weights are used for each nucleotide?

The calculator uses the average residue weights: dAMP = 313.21 g/mol, dTMP = 304.19 g/mol, dGMP = 329.21 g/mol, dCMP = 289.18 g/mol. These are the weights of the nucleotide residues within a phosphodiester chain (after loss of water during condensation).

Does the result include the water molecule at the ends?

Yes. A water molecule (18.02 g/mol) is added to the sum to account for the free 5'-OH and 3'-phosphate termini of the intact strand.

How is double-stranded (dsDNA) weight calculated?

The dsDNA weight is the sum of both complementary strands: the entered sequence plus its Watson-Crick complement (A↔T, G↔C). The calculator computes each strand independently and adds them.

Can I include ambiguous bases like N, R, or Y?

Ambiguous IUPAC codes are not supported. Only A, T, G, and C are recognized; all other characters are silently ignored. For sequences with ambiguous bases, the result reflects only the recognized bases.

What is the difference between Da and g/mol?

1 Da (dalton) equals 1 g/mol for a single molecule. The values are numerically identical — "Da" is used when describing the mass of one molecule, while "g/mol" describes the mass of one mole of molecules.

Molecular Weight of DNA Calculator

Name: Molecular Weight of DNA Calculator
Availability: InStock
Author: Nham Vu

Paste a DNA sequence to instantly calculate its molecular weight for single-stranded and double-stranded forms.

DNA Sequence

Only A, T, G, C are counted. Other characters are ignored. 0 bases

Strand type

Single-stranded (ssDNA) Double-stranded (dsDNA)

Sample sequences

Enter a DNA sequence and click Calculate

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Summary

Paste a DNA sequence to instantly calculate its molecular weight for single-stranded and double-stranded forms.

How it works

Paste or type your DNA sequence (A, T, G, C) into the input field.
Non-base characters are automatically stripped before calculation.
The calculator counts each A, T, G, and C in the sequence.
Each base is multiplied by its average monoisotopic residue weight.
The result accounts for the water molecule lost during phosphodiester bond formation.
Both single-stranded (ssDNA) and double-stranded (dsDNA) weights are displayed.

Use cases

Estimate the mass of a synthetic oligonucleotide before ordering.
Verify expected molecular weight of a PCR primer.
Determine how many moles are in a known mass of a DNA fragment.
Compare ssDNA and dsDNA weights for hybridization experiments.
Calculate the weight of a restriction enzyme cleavage product.
Quickly check the molecular weight during CRISPR guide RNA design.

Frequently Asked Questions

Last updated: 2026-07-01 · Reviewed by Nham Vu

Molecular Weight of DNA Calculator

DNA Sequence