Calculate m/z or neutral mass using charge, signed adduct shifts, stoichiometry, custom particle mass, approximate isotope spacing, and a charge ladder.

Neutral mass before the specified shift; use ion mass with count 0 for direct mass/charge.

Independent of |z|. Use 0 for no mass correction.

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M/Z Value Formula

For an ion mass already including its charge-related mass changes, use the following numerical ratio. The calculator also supports a specified signed shift from an unshifted mass.

m / z = M / |Z|

Variables:

  • M is the mass of the ion (daltons, Da)
  • |Z| is the positive magnitude of the ion charge in elementary-charge units

To calculate the m/z value, divide the ion mass in Da by the positive charge magnitude. For the calculator’s direct ion-mass example, select shift count 0; otherwise it applies m/z = (M + n × Δ) / |Z|.

What is an M/Z Value?

The m/z value is a dimensionless quantity that represents the mass-to-charge ratio of an ion. It is a fundamental parameter in mass spectrometry, which is a technique used to measure the masses of particles, the elemental composition of a sample, and the chemical structures of molecules. The m/z value helps in identifying and quantifying molecules in a sample.

How to Calculate M/Z Value?

The following steps outline how to calculate the m/z value.

  1. First, determine the mass of the ion (M) in daltons (Da).
  2. Next, determine the positive charge magnitude |Z| in elementary-charge units.
  3. Next, gather the formula from above: m/z = M / |Z|.
  4. Finally, calculate the m/z value.
  5. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge.

Mass of the ion (M) = 196 Da

Charge magnitude |Z| = 2; with ion mass 196 Da and shift count 0, m/z = 196 / 2 = 98.