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Protein Molecular Weight from Sequence Calculator — result sheet
Estimate a protein's average molecular mass from a one-letter amino-acid sequence, accounting for peptide-bond water loss and reporting daltons and kilodaltons.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: Protein molecular mass = sum of average residue masses + one water molecule; the residue masses already reflect peptide-bond condensation. Average residue mass = molecular mass ÷ residue count.
The sequence model adds the average mass of each amino-acid residue and one water molecule for the completed chain. It is intentionally transparent and composition-based; it does not infer post-translational modifications, signal-peptide cleavage, disulfide loss, oligomerization, isotope labeling, or an experimental mass-spectrum peak.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- One-letter amino-acid sequence — Use standard one-letter amino-acid codes; spaces and line breaks are ignored.
Worked example
| Input | Value |
|---|---|
| One-letter amino-acid sequence | MKWVTFISLLFLFSSAYSRGVFRR |
The 24-residue sequence is estimated at about 2,912.49 Da, or 2.91249 kDa, under the average-mass unmodified-chain convention.
Assumptions and limits
- The sequence uses the standard one-letter codes A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, and V.
- Whitespace is formatting and is removed before counting residues; other symbols are rejected rather than silently guessed.
- Average isotopic masses are used, not monoisotopic masses.
- One water molecule is added to the condensed chain and no additional chemical modification is included.
- The sequence represents one unmodified polypeptide chain and does not calculate a multimer mass.
- Use a sequence-analysis or mass-spectrometry workflow for an experimentally validated molecular mass.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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