Molecular Weight Calculator — Chemicals, Proteins, DNA & RNA

How This Molecular Weight Calculator Works

Chemical Formulas

When you input a formula like H₂O or C₁₂H₂₂O₁₁, the calculator parses each element, multiplies by its atomic weight (IUPAC averages), and sums the total. It supports simple parentheses such as Fe(OH)₃.

Protein, DNA, and RNA Sequences

The tool detects sequence type from one-letter codes and ambiguity codes (IUPAC):

• Protein: A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y, V (+ B, Z, X, J)
• DNA: A, T, C, G (R, Y, S, W, K, M, B, D, H, V, N)
• RNA: A, U, C, G (R, Y, S, W, K, M, B, D, H, V, N)

Residue weights are average literature values and account for polymerization (loss of H₂O per bond). One terminal H₂O is added back to represent intact ends.

Example Molecular Weight Calculations

• C₆H₁₂O₆ (glucose) → ~180.156 g/mol
• NaCl (sodium chloride) → ~58.44 g/mol
• Protein sequence: AGYWCF → calculated from average amino-acid residue weights + terminal water
• DNA sequence: ATGCGT → calculated as a polymer from base-specific residue weights + terminal water

Common pitfalls & tips

• Capitalization matters: Co (cobalt) ≠ CO (carbon monoxide).
• Parentheses: Supported for simple groups like (OH)₂; nested or complex brackets aren’t supported in this version.
• Isotopic/monoisotopic masses: Uses average atomic/residue weights; exact isotopologues and charge states are out of scope.
• Mixed sequences: Inputs containing both T and U are ambiguous and will return an error.

Frequently Asked Questions

Does this work for proteins and nucleic acids?

Yes. The calculator detects sequence type automatically and applies average residue weights for proteins, DNA, and RNA.

Are my inputs private?

All calculations happen in your browser. Nothing is uploaded or stored—ideal for proprietary or unpublished research.

Does it support formulas with parentheses?

Yes. It handles basic parentheses such as (OH)₂, though nested parentheses are not supported in this version.