What is the degree of polymerization?

The degree of polymerization (DP or Xn) is the number of repeat units (monomer units) in a single polymer chain. It equals the polymer molecular weight divided by the molecular weight of one repeat unit.

What molecular weight should I use — Mn or Mw?

Use the number-average molecular weight (Mn) to get the number-average degree of polymerization (DPn). Using Mw gives the weight-average DP (DPw). GPC reports both; Mn is most common for DP calculations.

What is the monomer molecular weight for common polymers?

Common values: polyethylene repeat unit (CH2-CH2) = 28.05 g/mol, polystyrene repeat unit = 104.15 g/mol, poly(methyl methacrylate) = 100.12 g/mol, poly(lactic acid) = 72.06 g/mol.

What is the end-group correction?

Polymer chains have two chain ends that are not repeat units (e.g., initiator fragments). Their combined molecular weight is the end-group weight. For high-MW polymers this is negligible, but for oligomers it matters: DP = (Mn - Mend) / M0.

What DP range is considered a polymer vs. oligomer?

Oligomers typically have DP from 2 to ~20. Low polymers: 20–100. High polymers: 100–10,000. Ultra-high molecular weight polymers exceed 10,000 repeat units.

Degree Of Polymerization

Name: Degree Of Polymerization
Availability: InStock
Author: Nham Vu

Enter polymer molecular weight and monomer (repeat unit) molecular weight to instantly calculate the degree of polymerization.

Polymer Inputs

Number-Average Molecular Weight, Mn

g/mol

Repeat Unit (Monomer) Molecular Weight, M₀

g/mol

End-Group Molecular Weight (optional)

g/mol

Combined weight of both chain-end groups. Leave 0 if unknown.

Common Repeat Units

Results

Enter values and click Calculate DP.

DP Classification Reference

Type	DP Range
Dimer / Trimer	2 – 3
Oligomer	4 – 20
Low polymer	21 – 100
High polymer	101 – 10,000
Ultra-high MW	> 10,000

Copied!

Summary

Enter polymer molecular weight and monomer (repeat unit) molecular weight to instantly calculate the degree of polymerization.

How it works

Enter the number-average molecular weight (Mn) of the polymer in g/mol.
Enter the molecular weight of the monomer (repeat unit) in g/mol.
Optionally specify end-group molecular weight if known (default 0).
The calculator divides (Mn minus end-group weight) by monomer molecular weight.
Results include DP, estimated chain length category, and formula reference.

Use cases

Determine chain length from GPC or osmometry Mn data.
Compare DP across different polymerization batches.
Estimate physical property trends (viscosity, tensile strength) from DP.
Teaching polymer chemistry concepts and stoichiometry.
Quality control checks in industrial polymer production.
Convert between molecular weight and repeat-unit count for literature comparisons.

Frequently Asked Questions

Related tools

Molecular Weight Polymer Crystallinity Percent Glass Transition Helper

Last updated: 2026-05-28 · Reviewed by Nham Vu