TPSA Calculator

In short: TPSA calculator for SMILES or compound names. It is free, works in your web browser and needs no download.

Enter a SMILES string or compound name to retrieve topological polar surface area (TPSA), a common medicinal chemistry property for permeability and oral bioavailability screening.

What TPSA Tells You

TPSA estimates the polar surface contributed by hetero atoms and attached hydrogens. In Veber-style oral bioavailability guidelines, TPSA at or below about 140 A^2 is often considered favorable, although context matters.

Interpreting TPSA

Topological polar surface area (TPSA) adds up surface contributions from polar atoms, mainly oxygen and nitrogen and the hydrogens attached to them. Ertl and colleagues introduced the fragment-based method in 2000 so the value can be computed from the 2D structure alone, without generating a 3D model. That makes it fast enough to screen large libraries.

Commonly used thresholds

• 140 Ų or less: part of Veber's criteria associated with good oral bioavailability in rats.
• About 90 Ų or less: often cited for compounds intended to cross the blood–brain barrier.

Examples

• Aspirin: about 63.6 Ų (an ester and a carboxylic acid).
• Ibuprofen: about 37.3 Ų (one carboxylic acid).
• Glucose: about 110 Ų (five hydroxyl groups and a ring oxygen).

Keep in mind: TPSA ignores sulfur and phosphorus in its standard form, and it is a guide, not a measurement of permeability. Use it together with logP and molecular weight, for example in the Druglikeness Calculator.