Use our isotope calculator calculator for quick and accurate calculations. Free online tool.
An isotope calculator helps you explore atomic variants of the same element that share the same number of protons (atomic number Z) but differ in the number of neutrons (N). Isotopes of an element are chemically nearly identical but can have very different nuclear stability and radioactive properties.
For example, carbon has three naturally occurring isotopes: ¹²C (6 protons, 6 neutrons), ¹³C (6 protons, 7 neutrons), and ¹⁴C (6 protons, 8 neutrons). While ¹²C and ¹³C are stable, ¹⁴C is radioactive and is used in carbon dating.
Enter the element symbol or atomic number and the mass number to retrieve key isotope data: number of neutrons, nuclear spin, natural abundance, half-life (for radioactive isotopes), and common applications in medicine, industry, and research.
Isotopes, atomic mass, mass number, neutrons, and nuclear binding energy
Explore CategoryIsotopes are atoms of the same element with the same number of protons but a different number of neutrons, giving them different mass numbers while sharing virtually identical chemical behavior.
Enter the element symbol and the desired mass number (A); the calculator will compute the neutron count as N = A − Z and display available nuclear data for that nuclide.
No. Many isotopes are stable, such as ¹H, ¹²C, and ¹⁶O. Radioactive (unstable) isotopes decay over time by emitting alpha, beta, or gamma radiation.
Protium (¹H) makes up about 99.98% of natural hydrogen; deuterium (²H) accounts for ~0.02%, and tritium (³H) is a rare radioactive isotope.
Radioactive isotopes like Tc-99m are used in nuclear imaging (PET/SPECT scans), while stable isotopes such as ¹³C are used in breath tests and metabolic studies.