Self-Assembly Calculator

Packing parameter and predicted self-assembled structure.

Inputs

Tail Volume (nm³)

Head Group Area (nm²)

Tail Length (nm)

Temperature (°C)

Concentration (mM)

Tab to move between fields

Results

Packing Parameter (p)

0.32

Structure (1-5)

1

Aggregation Number56

Micelle Radius (nm)1.7

Bilayer Thickness (nm)0

Estimated CMC (mM)8

Above CMC? (1=Yes)1

How to Use This Calculator

Enter amphiphile tail volume (nm³), head group area (nm²), and tail length (nm).
Set the solution temperature (°C) and concentration (mM).
Review the packing parameter (p) — values below 0.33 favor spherical micelles, 0.33–0.5 favor cylinders, above 0.5 favor bilayers.
Check the predicted self-assembled structure type, aggregation number, and micelle radius (nm).
Adjust tail length or head group area (via pH or ionic strength) to tune the target nanostructure.

How the result changes with Head Group Area (nm²)

Head Group Area (nm²)	Packing Parameter (p)	Structure (1-5)
0.51	0.4	2
1.76	0.12	1
3.25	0.06	1
4.5	0.05	1

What each input means

Tail Volume (nm³): Hydrophobic tail volume. C12: ~0.35 nm³.
Head Group Area (nm²): Effective head group cross-section. SDS: ~0.62 nm².
Tail Length (nm): Fully extended hydrocarbon tail length. C12: ~1.67 nm.
Temperature (°C): Solution temperature.
Concentration (mM): Surfactant concentration in millimolar.

What each result means

Packing Parameter (p): p = v/(a·l). Determines self-assembled structure.
Structure (1-5): 1=sphere, 2=cylinder, 3=vesicle, 4=bilayer, 5=inverted.
Aggregation Number: Molecules per micelle (spherical only).
Micelle Radius (nm): Spherical micelle radius ~ tail length.
Bilayer Thickness (nm): Bilayer thickness ~ 2× tail length.
Estimated CMC (mM): Rough CMC estimate (SDS-like baseline).
Above CMC? (1=Yes): Whether concentration exceeds estimated CMC.

How this is calculated

Worked example, using the default values

Identify Input Parameters
4 parameters
Tail Volume (nm³) = 0.35, Head Group Area (nm²) = 0.65, Tail Length (nm) = 1.7, Temperature (°C) = 25 = 5 input(s) provided
Calculate Packing Parameter
Packing Parameter = tailVolumeNm3 / (headAreaNm2 * tailLengthNm)
0.3167 = 0.3167
Calculate Structure
1 = 1
Calculate Aggregation Number
Aggregation Number
56 = 56
Calculate Micelle Radius
1.7 = 1.7

Engine last updated July 26, 2026. Checked against 3 independently-derived tests — how we verify calculators.

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