Peptides Calculator
Calculate the molecular weight, extinction coefficient, and concentration of a peptide sequence. Useful for researchers and biochemists.
Published by:
isCalculator Editorial Team
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How to use this tool?
How to Use the Peptides Calculator
- Enter the peptide sequence in the "Peptide Sequence" field using single-letter amino acid codes (e.g.,
ACDEFGH). Only uppercase letters A–Z are accepted. - Optional: Enter absorbance at 280 nm in the "Absorbance (280 nm)" field. Leave blank if not needed.
- Set path length in centimeters (default is 1 cm). Must be a positive number.
- Click Calculate or press Enter.
Results shown:
- Molecular Weight – sum of residue weights plus water (18.02 Da).
- Extinction Coefficient – based on Trp (5500), Tyr (1490), and cystine pairs (125 each).
- Concentration – in mg/mL (only if absorbance is provided). Formula: (Abs × MW) / (Ext × path length).
Note: All values use metric units. Ensure the sequence contains only standard amino acids (A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y, V).
Previous Results
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Frequently Asked Questions
Standard single-letter codes: A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, Y.
Sum of residue weights plus the weight of a water molecule (18.02 Da).
Based on contributions from tryptophan (5500 M⁻¹cm⁻¹), tyrosine (1490 M⁻¹cm⁻¹), and cystine (125 M⁻¹cm⁻¹ per disulfide bond).