log p calculator

What is logP?

logP is the base-10 logarithm of a compound’s partition coefficient between octanol and water. It describes how strongly a neutral compound prefers a nonpolar phase (octanol, a proxy for lipids) versus an aqueous phase (water). In chemistry, medicinal chemistry, and environmental science, logP is a core descriptor for lipophilicity.

In short: higher logP usually means the molecule is more lipophilic (fat-loving), while lower or negative logP means it is more hydrophilic (water-loving).

Key formula used in this calculator

Step 1: Compute partition coefficient (P)

P = Coctanol / Cwater

Here, both concentrations should be measured at equilibrium and in the same units.

Step 2: Convert to logarithmic scale

logP = log10(P)

Because P values can vary over several orders of magnitude, the log scale makes interpretation easier.

How to use this log p calculator

• Mode 1: Enter concentrations in octanol and water to compute both P and logP.
• Mode 2: Enter P directly to compute logP.
• Mode 3: Enter logP to compute P.

The calculator also gives a quick interpretation of lipophilicity so you can contextualize the number right away.

How to interpret logP values

• logP < 0: Mostly hydrophilic; tends to prefer water.
• 0 to 1: Slight lipophilicity.
• 1 to 3: Moderate lipophilicity (often useful in drug design).
• 3 to 5: High lipophilicity; can reduce aqueous solubility.
• > 5: Very lipophilic; may present formulation or bioavailability challenges.

logP vs logD (important distinction)

People often mix up logP and logD. They are related but not identical:

• logP: for the neutral form of a compound.
• logD: pH-dependent distribution including ionized and neutral species.

If your compound is ionizable, logD at physiological pH can be more predictive for real biological behavior.

Practical use cases

Medicinal chemistry

logP helps estimate membrane permeability, absorption potential, and general balance between solubility and permeability.

Environmental chemistry

Compounds with higher logP are often more likely to partition into sediments, organic matter, and biota, which can influence bioaccumulation risk.

Analytical and formulation work

logP informs solvent selection, extraction behavior, and early-stage formulation strategies.

Tips for better calculations

1. Use equilibrium concentrations from a validated shake-flask or equivalent method.
2. Keep units consistent between phases.
3. Make sure values are positive and non-zero for concentration-based calculations.
4. Remember that temperature, pH, and ionic strength can affect observed behavior.

Final takeaway

A reliable logP estimate can save time in compound prioritization, screening, and risk assessment. Use this calculator for fast conversions and quick interpretation, then pair the result with pKa, logD, and experimental context for stronger decisions.