LogP Calculator

Illustrative sample replicates showing how Co, Cw, and logP relate.

• Direct partition: logP = log10(Co / Cw), where Co is octanol concentration and Cw is water concentration.
• Blank correction (optional): Co' = Co − blank, Cw' = Cw − blank, then compute logP using Co' and Cw'.
• Replicates: Mean logP, sample SD, CV%, and 95% CI (t-based) are calculated from replicate logP values.
• pH-corrected from logD: Uses a monoprotic approximation to estimate neutral logP from logD, pH, and pKa.

1. Select Direct (Co and Cw) or pH-corrected (from logD).
2. For direct mode, enter up to five Co and Cw replicates using the same units.
3. Optionally enter a blank correction if you measured background signal.
4. If you want a quick recovery check, add C0, Vo, and Vw.
5. Press Calculate logP. The results appear above the form.
6. Use the download buttons to export CSV or PDF reports.

1) What does logP represent?

logP is the base‑10 logarithm of a compound’s partition between octanol and water. Higher values usually mean more lipophilicity and stronger preference for nonpolar environments.

2) What is the difference between logP and logD?

logP describes the neutral form’s partitioning. logD is measured at a given pH and includes ionized species. For ionizable compounds, logD can change significantly with pH.

3) Do Co and Cw need the same units?

Yes. The ratio Co/Cw is unitless only when both concentrations share the same units. If units differ, convert them first to avoid misleading logP values.

4) Why include replicate measurements?

Replicates improve reliability. The calculator summarizes variability using SD and CV%. If you provide at least two replicates, it also estimates a 95% confidence interval for the mean logP.

5) When should I use blank correction?

Use it when your analytical method shows background signal. Subtract the blank from Co and Cw before computing the ratio. Ensure corrected concentrations remain positive.

6) How does the pH correction work in logD mode?

For monoprotic acids or bases, the calculator adds a log10 term that accounts for ionization at the chosen pH. This estimates the neutral logP from logD, pH, and pKa.

7) What is the recovery percentage?

Recovery compares total amount found in both phases to the starting amount from C0 and volumes. It is a simple mass balance indicator. Large deviations can suggest loss, adsorption, or measurement drift.

8) How should I interpret very high logP values?

Very high logP can indicate strong lipophilicity, but it may also reflect solubility limits, emulsion formation, or analytical saturation. Check experimental conditions, ensure equilibrium, and verify concentrations are within the method’s linear range.