Protein Molecular Weight

Protein sequences

Output

How to calculate the molecular weight of a protein

Paste one or more protein sequences, as plain text or FASTA.
The molecular weight appears in daltons and kDa, with the extinction coefficient at 280 nm.
Copy output or Download saves the result.

Frequently asked questions

How is the extinction coefficient worked out?

From the number of tryptophans (5500 each) and tyrosines (1490 each), plus 125 for each cystine when all cysteines form disulfide bonds. Both values are shown.

Is this the average or monoisotopic mass?

The average mass, from the average residue masses plus one water.

Is my sequence uploaded?

No. Everything runs in your browser, so your sequences never leave your device.

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