Polymer Molecular Weight Calculator
This polymer sample has a number-average molecular weight of 27000 g/mol and a weight-average of 30,000 g/mol, a polydispersity of 1.11.
Polyethylene −CH₂CH₂− 28.05, PVC 62.50, polystyrene 104.15.
27000 g/mol
- Weight-average molecular weight M_w
- 30000 g/mol
- Polydispersity index M_w/Mₙ
- 1.111111111
- Degree of polymerisation Mₙ/m₀
- 962.5668449
Step-by-step solution
- Mₙ = Σ xᵢMᵢ ÷ Σ xᵢ = 27000 g/mol
- M_w = Σ xᵢMᵢ² ÷ Σ xᵢMᵢ = 30000 g/mol
- PDI = 1.111111111
Polymer Molecular Weight Formula
Mₙ = Σ xᵢMᵢ, M_w = Σ xᵢMᵢ² / Σ xᵢMᵢ
xᵢ number fraction; PDI = M_w/Mₙ ≥ 1; DP = Mₙ/m₀
Worked Example
Fractions of 10, 20, 30 and 40 kg/mol with number fractions 0.1, 0.3, 0.4 and 0.2:
- Mₙ = Σ xᵢMᵢ ÷ Σ xᵢ = 27000 g/mol
- M_w = Σ xᵢMᵢ² ÷ Σ xᵢMᵢ = 30000 g/mol
- PDI = 1.111111111
Polydispersity index M_w/Mₙ: 1.111111111 · Degree of polymerisation Mₙ/m₀: 962.5668449
GATE tip
Degree of polymerisation uses the repeat unit’s mass: polyethylene (C₂H₄)ₙ has m₀ = 28.05 g/mol, PVC 62.50, polystyrene 104.15.
More Processing and Materials Calculators
-
Rule of Mixtures Calculator
Isostrain: E_c = V_fE_f + V_mE_m
isostress: 1/E_c = V_f/E_f + V_m/E_m
Example: Carbon fibre (230 GPa) in epoxy (3.5 GPa) at 60 % fibre volume: Longitudinal modulus (isostrain) E_c = 139.4 GPa.
-
Radius Ratio Calculator
r_c / r_a → coordination number
limits 0.155 (3), 0.225 (4), 0.414 (6), 0.732 (8), 1.0 (12)
Example: Sodium chloride: Na⁺ 1.02 Å and Cl⁻ 1.81 Å: Radius ratio r_c/r_a = 0.563536.
-
Rolling Calculator
Δh_max = μ²R, L = √(RΔh)
F ≈ σ̄ w L (no friction hill); true strain ln(h₀/h₁)
Example: Rolling 25 mm plate to 20 mm with 300 mm radius rolls and μ = 0.1: Draft Δh = 5 mm.
-
Chvorinov's Rule Calculator
t = B (V/A)ⁿ
B mould constant, n ≈ 2; riser modulus ≥ 1.2 × casting modulus
Example: A 200 × 100 × 50 mm block with B = 2 s/mm² and n = 2: Solidification time t = 6.80272 min.
Frequently asked questions
Why is M_w always at least Mₙ?
M_w weights each chain by its mass, so heavy chains count more; they are equal only when every chain is the same length.
How do I use weight fractions instead?
With weight fractions wᵢ: M_w = Σ wᵢMᵢ and 1/Mₙ = Σ wᵢ/Mᵢ.
Sources
- The International System of Units (SI), 9th edition (SI Brochure), Bureau International des Poids et Mesures .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Polymer Molecular Weight Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/polymer-molecular-weight-calculator/
IEEE
Scientific Converters, "Polymer Molecular Weight Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/polymer-molecular-weight-calculator/