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

Chain counts by mass bin

Required list input.

Molar masses by bin

Required list input.

Calculate Mw=ΣNiMi²/ΣNiMi from a polymer chain-count distribution. Heavy chains contribute disproportionately, so Mw is normally at least Mn for the same distribution. 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]

Polymer Weight-Average Molecular Mass

The resulting polymer weight-average molecular mass returned as a number.

• Polymer averages and dispersity depend on the molecular-weight distribution and measurement method. Branching, copolymers, end groups, conversion, degradation, and calibration standards can make ideal chain relationships incomplete.
• 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.

• Polymer Number-Average Molecular Mass

  Calculate Mn=ΣNiMi/ΣNi from counts of polymer chains in each molar-mass bin. Counts and masses must have equal, nonempty lengths; masses should use a consistent unit.

• Polymer Dispersity

  Calculate polymer dispersity Đ=Mw/Mn from weight-average and number-average molar masses. For a valid nonnegative molecular-weight distribution, Mw should not be below Mn.

• 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.