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⚛️ Atomic Mass Calculator

Calculate average atomic mass from isotope data and lookup atomic masses

Average Atomic Mass from Isotopes

Element Lookup

Molecular Mass Calculator

Mass Conversion

Atomic Mass Reference Guide

Key Concepts:

Atomic Mass Unit (amu):

1 amu = 1.66054 × 10⁻²⁴ g. Based on 1/12 the mass of a carbon-12 atom.

Average Atomic Mass:

Weighted average of all isotope masses based on their natural abundances.

Molecular Mass:

Sum of all atomic masses in a molecule (also called molecular weight).

Common Atomic Masses (amu):

H
1.008
C
12.01
N
14.01
O
16.00
Na
22.99
Cl
35.45

Calculation Formula:

Average Atomic Mass = Σ (Isotope Mass × Fractional Abundance)

Where fractional abundance = percentage / 100

Mass Conversion Factors:

  • 1 amu = 1.66054 × 10⁻²⁴ g
  • 1 g = 6.02214 × 10²³ amu
  • Avogadro's Number = 6.02214 × 10²³ particles/mol
  • 1 mole of atoms = atomic mass in grams