LogP Calculator
In short: LogP 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 PubChem XLogP, a hydrophobicity estimate used in medicinal chemistry and formulation screening.
What LogP Tells You
LogP estimates the partitioning of a neutral compound between octanol and water. Higher LogP generally means a compound is more hydrophobic; very high values can indicate lower aqueous solubility and possible permeability/formulation tradeoffs.
Interpreting logP values
logP is the base-10 logarithm of the octanol/water partition coefficient of the neutral form of a compound. A logP of 2 means the compound is about 100 times more concentrated in octanol than in water at equilibrium. XLogP, the value PubChem provides, is a computed estimate based on atom and fragment contributions, not a measurement.
Rough guide
- Below 0: hydrophilic. Sugars such as glucose are strongly negative.
- About 1 to 3: a common range for orally absorbed drugs.
- Above 5: very lipophilic; poor solubility is more likely, and it is one of Lipinski's flags.
logP versus logD
logP describes the neutral molecule only. Acids and bases ionise in water depending on pH, so the measured distribution at a given pH (logD) can be much lower than logP. For a carboxylic acid at pH 7.4, most molecules are ionised, so logD is typically well below logP.
Tip: compare analogues in a series rather than relying on one absolute number; the change in logP when you add a group is often more informative. See also the Druglikeness Calculator.
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