Convert LopP to P, perform an Octanol/Water split, or calculate the coefficient from measured concentrations.

LogP + Partition Coefficient Calculator

Use the tab that matches your goal: convert LogP and P, estimate how a compound splits between octanol and water, or calculate LogP from measured equilibrium concentrations.

Convert LogP and P Best for quick lookups and property conversion.
Octanol/Water Split Estimate how much ends up in each phase.
From Measured Concentrations Use equilibrium concentrations in octanol and water.
Convert LogP and Partition Coefficient
Enter either LogP or P. The calculator returns both values and a quick interpretation of lipophilicity.

Understanding LogP and the Partition Coefficient

The partition coefficient describes how a compound distributes between an organic phase and an aqueous phase after equilibrium is reached. This calculator first finds the partition coefficient P, then converts it to logP. Larger values indicate stronger preference for the organic phase, while smaller values indicate stronger preference for water.

P = \frac{C_{organic}}{C_{aqueous}}
\log P = \log_{10}(P)
Quantity What it means How to read it
P Ratio of concentration in the organic phase to concentration in the aqueous phase P > 1: favors organic phase
P = 1: equal distribution
P < 1: favors aqueous phase
logP Base-10 logarithm of P Positive: more lipophilic
Zero: evenly partitioned
Negative: more hydrophilic

Quick reference values

P = 10^{\log P}
logP P Interpretation
-1 0.1 About 10x more concentrated in the aqueous phase
0 1 Equal concentration in both phases
0.5 3.16 Moderate preference for the organic phase
1 10 About 10x more concentrated in the organic phase
2 100 Strong organic-phase preference
3 1000 Very strong organic-phase preference

How to use this calculator correctly

  1. Measure the compound concentration in the organic phase after equilibrium.
  2. Measure the compound concentration in the aqueous phase after equilibrium.
  3. Enter both values using the same unit system (mg/L with mg/L, g/L with g/L, or mol/L with mol/L).
  4. The calculator returns both P and logP.

Important: The ratio is only meaningful when both concentrations are expressed on the same basis. If the units do not match, the result is not valid.

Why logP is useful

Application Why it matters
Drug discovery Helps assess lipophilicity, membrane permeability, and formulation tradeoffs
Liquid-liquid extraction Shows which phase is likely to retain more of the solute
Environmental chemistry Helps estimate whether a substance prefers water or more hydrophobic environments
Analytical chemistry Useful for designing separations and solvent systems

Common mistakes to avoid

Mistake Why it causes problems
Using different units in each phase The ratio no longer represents a true partition coefficient
Using concentrations before equilibrium P is defined from equilibrium concentrations
Entering zero or negative values logP requires a positive ratio
Comparing values from different solvent systems Partition behavior depends on the specific organic/aqueous pair used
Confusing logP with logD For ionizable compounds, pH can change observed distribution

LogP vs. logD

Term Best used for Key point
logP Neutral-compound partitioning Represents intrinsic preference between organic and aqueous phases
logD Ionizable compounds at a specific pH Changes with pH because ionized and neutral forms distribute differently

If the compound can ionize in water, logD at a stated pH is often more informative than logP alone.

Example calculation

If the concentration in the organic phase is 65 mg/L and the concentration in the aqueous phase is 30 mg/L:

P = \frac{65}{30} = 2.1667
\log P = \log_{10}(2.1667) \approx 0.336

This result indicates the compound is somewhat more concentrated in the organic phase than in the aqueous phase.

Practical interpretation guide

General range Typical behavior
logP < 0 Strong preference for water; usually quite hydrophilic
0 to 1 Low to mild lipophilicity
1 to 3 Moderate lipophilicity
3 to 5 High lipophilicity; often much more soluble in nonpolar environments
> 5 Very hydrophobic behavior; interpretation should be made carefully in context

For best results, use measured equilibrium concentrations, keep the unit basis consistent, and interpret the number alongside solvent choice, pH, and the chemical properties of the compound being tested.