KatzLab Molecular Analytics
Easy Peasy Exact Mass Calculator
Charge / adducts
Add one row per contribution. Negative ions can be from removals (e.g., −H = deprotonation),
additions of anions (e.g., +Cl−), or combinations (e.g., +FA− is effectively +formate).
“Charge only” affects z but adds 0 mass (useful for fixed charges like SAM).
“Charge only” affects z but adds 0 mass (useful for fixed charges like SAM).
Count
Type
±
We compute: z = Σ(countᵢ · signᵢ) and
m/z = (M + Σ(massContribᵢ)) / |z| (if z ≠ 0).
Note: some entries represent removal (negative mass contribution), e.g. −H (deprotonation).
Note: some entries represent removal (negative mass contribution), e.g. −H (deprotonation).
Formula parser is strict about element symbols (e.g., Cl, not CL).
Result
—
Enter a formula.
Parsed composition
| Part | Count | Mono mass each | Subtotal |
|---|---|---|---|
| — | |||
Notes
• Monoisotopic mass uses common isotopes (e.g., 12C, 1H, 16O).
• Isotopes like [13]C override default element mass.
• Deprotonation (−H) subtracts a proton mass and contributes −1 charge.
• Isotopes like [13]C override default element mass.
• Deprotonation (−H) subtracts a proton mass and contributes −1 charge.