Estimate protein mass in daltons and kilodaltons from amino acid count for quick lab planning.
MW ≈ amino acids × 110 DaA common quick estimate is that each amino acid residue contributes about 110 daltons after peptide-bond formation. Divide daltons by 1,000 to convert the estimate to kilodaltons.
| Symbol | Variable | Description |
|---|---|---|
| aa | Amino acid count | The number of residues in the protein sequence. |
| Da | Daltons | A molecular mass unit commonly used for proteins. |
| kDa | Kilodaltons | 1 kDa equals 1,000 Da. |
Enter sequence length
Use the number of amino acid residues in the mature protein or construct you want to estimate.
Calculate mass
The calculator multiplies amino acid count by the average residue mass of about 110 Da.
Use kDa for lab context
Read the kDa estimate when choosing gel percentage, ladder range, tags, or purification expectations.
This protein molecular weight calculator is best for quick estimates before you look up exact sequence mass. A 100 amino acid peptide is roughly 11 kDa, a 300 amino acid protein is roughly 33 kDa, and a 500 amino acid protein is roughly 55 kDa.
| Amino acids | Estimated mass |
|---|---|
| 100 aa | 11 kDa |
| 250 aa | 27.5 kDa |
| 300 aa | 33 kDa |
| 500 aa | 55 kDa |
| 1,000 aa | 110 kDa |
The 110 Da rule is useful for gel planning, quick construct checks, and approximate protein size. Exact molecular weight depends on the actual amino acid sequence, signal peptide cleavage, tags, disulfides, modifications, and isotope composition.
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