Use this chemistry calculator to reproduce a named relationship with explicit quantities and units for study, laboratory planning, or an independent numerical check.

Isotope masses (u)

Isotope masses in atomic mass units.

Abundances (%)

Percent abundance of each isotope.

Compute the weighted-average atomic mass from isotope masses and their percent abundances. The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Average mass (u)

Weighted-average atomic mass.

• Radioactive and nuclear calculations require the correct isotope, decay mode, mass convention, and time unit. Branching, daughter products, detector efficiency, shielding, and uncertainty in tabulated nuclear data may require a fuller model.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check units and significant figures, compare the result with limiting cases, and use measured or source-specific constants where available. Laboratory, safety, and regulatory decisions require validated methods and appropriate uncertainty analysis.

• Isotopic Abundance Calculator

  Solve the two-isotope percent abundances that produce a known weighted-average atomic mass.

• Isotope Pattern Ratio

  Estimate the M+1 to M peak intensity ratio from carbon count times 0.011 for natural 13C abundance of 1.1 percent.

• Number-Average Degree of Polymerization

  Estimate number-average polymerization degree as number-average molecular mass divided by repeat-unit molar mass. Both masses must use the same unit; end-group mass is neglected.