DNA/RNA Molecular Weight Calculator

The DNA/RNA Molecular Weight Calculator computes the exact mass of a nucleotide sequence in Daltons — useful for lab work involving oligonucleotide synthesis, gel analysis, or molecular cloning. Enter your nucleotide sequence (A, T, C, G for DNA or A, U, C, G for RNA), select the sequence type, strand type (single or double), and 5' end state to get the molecular weight in Da. Secondary outputs include sequence length, GC content, and a full nucleotide base count breakdown.

Enter DNA (A, T, C, G) or RNA (A, U, C, G) sequence. Numbers and spaces will be ignored.

Sequence Type *

Strand Type *

5' End State *

Results

Molecular Weight

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Sequence Length

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GC Content

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A Count

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T/U Count

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C Count

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G Count

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Frequently Asked Questions

What is the difference between DNA and RNA molecular weight calculations?

DNA contains deoxyribose sugar and thymine (T), while RNA contains ribose sugar and uracil (U). RNA is slightly heavier due to the extra hydroxyl group on ribose. The molecular weights are: A=313.2 (DNA)/329.2 (RNA), T=304.2 (DNA)/U=306.2 (RNA), C=289.2 (DNA)/305.2 (RNA), G=329.2 (DNA)/345.2 (RNA).

How does the 5' end phosphorylation affect molecular weight?

The 5' end state significantly impacts molecular weight. A 5' hydroxyl adds minimal weight, a 5' phosphate adds approximately 80 Da, and a 5' triphosphate adds about 159 Da to the total molecular weight of the sequence.

What characters are ignored in the sequence input?

The calculator ignores numbers, spaces, and any characters that don't correspond to valid nucleotide bases (A, T, C, G for DNA or A, U, C, G for RNA). Characters like B, Z, or N are filtered out automatically.

How is GC content calculated?

GC content is calculated as the percentage of guanine (G) and cytosine (C) bases in the total sequence. It's calculated as: (G count + C count) / total nucleotides × 100%. GC content affects DNA melting temperature and stability.

What is the accuracy of the molecular weight calculations?

The calculations use IUPAC standard atomic weights: H=1.00794, C=12.0107, N=14.0067, O=15.9994, P=30.973761 Da. Results are rounded to the nearest hundredth of a Dalton, providing accuracy far beyond typical laboratory requirements.

How does double-strand DNA affect the molecular weight?

For double-stranded DNA, the calculator determines the complement sequence and calculates the total weight of both strands. The complementary strand follows base-pairing rules: A pairs with T, and G pairs with C.

Can I use this calculator for modified nucleotides?

This calculator is designed for standard DNA and RNA nucleotides (A, T/U, C, G). Modified nucleotides, unusual bases, or chemical modifications are not supported and should be calculated separately.

What units are used for molecular weight results?

Molecular weight is reported in Daltons (Da), which is equivalent to atomic mass units (amu) or grams per mole (g/mol). One Dalton equals approximately 1.66 × 10⁻²⁷ kilograms.