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Polymer Degree Of Polymerisation Calculator

Work out polymer degree of polymerisation instantly with clear inputs, formula shown and shareable results.

About Polymer Degree Of Polymerisation Calculator

Degree of polymerisation is the number of repeat units per chain, so it is the number-average molar mass divided by the repeat unit's molar mass. Polystyrene at Mn = 250,000 with a 104.15 g/mol styrene unit averages about 2400 units. The Carothers equation gives an independent prediction from conversion alone, DP = 1/(1-p), which shows why step-growth polymers need conversions above 99% to reach useful chain lengths.

Formulas

From molar mass

DP = Mn / M0

Carothers equation

DP = 1 / (1 - p)

Worked example

With the default values below, Polymer Degree Of Polymerisation Calculator returns Degree Of Polymerisation of 2,400.4. Change any input above and every figure here is recalculated in your browser.

Inputs used

Number-average molar mass Mnminimum 0 g/mol
250,000 g/mol
Molar mass of the repeat unitminimum 0 g/mol
104.15 g/mol
Monomer conversion reachedaccepts 0–1
0.99

Results

Degree Of Polymerisation
2,400.4
Degree Predicted By Carothers From Conversion
100.00
Chains Per Gram
2.4089 × 10¹⁸
Backbone Carbon Atoms Per Chain
4,800.8

Step by step

  1. 1Values used
  2. 2From molar mass
  3. 3Carothers equation
  4. 4Degree Of Polymerisation= 2,400.4
  5. 5Degree Predicted By Carothers From Conversion= 100.00
  6. 6Chains Per Gram= 2,408,860,000,000,000,000.0000
  7. 7Backbone Carbon Atoms Per Chain= 4,800.8

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why do the two estimates disagree?

Carothers applies to step-growth polymerisation at a given conversion; the mass route reflects what the chains actually are. A gap points to chain transfer or a chain-growth mechanism.

Does this tell me the polydispersity?

No - that needs the weight-average mass as well. PDI = Mw/Mn, and it is 1 for a perfectly uniform sample.

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