The article introduces the *Brain Or Intestinal Estimated Permeation* (BOILED-Egg) method, a predictive model for estimating the gastrointestinal absorption and brain penetration of small molecules. The model is based on the lipophilicity and polarity of these molecules, using the *n*-octanol/water partition coefficient (log *P*) and polar surface area (PSA) as key descriptors. The authors curated datasets of human intestinal absorption (HIA) and blood-brain barrier (BBB) permeation to optimize the model's accuracy. The BOILED-Egg model provides a clear, graphical representation of the physicochemical space, with the white region indicating high gastrointestinal absorption and the yellow region (yolk) indicating high BBB permeation. The model's internal accuracy is 93% for gastrointestinal absorption and 90% for BBB permeation, with cross-validation showing robustness and high predictive power. The BOILED-Egg is useful for drug discovery and development, aiding in lead optimization and improving pharmacokinetics.The article introduces the *Brain Or Intestinal Estimated Permeation* (BOILED-Egg) method, a predictive model for estimating the gastrointestinal absorption and brain penetration of small molecules. The model is based on the lipophilicity and polarity of these molecules, using the *n*-octanol/water partition coefficient (log *P*) and polar surface area (PSA) as key descriptors. The authors curated datasets of human intestinal absorption (HIA) and blood-brain barrier (BBB) permeation to optimize the model's accuracy. The BOILED-Egg model provides a clear, graphical representation of the physicochemical space, with the white region indicating high gastrointestinal absorption and the yellow region (yolk) indicating high BBB permeation. The model's internal accuracy is 93% for gastrointestinal absorption and 90% for BBB permeation, with cross-validation showing robustness and high predictive power. The BOILED-Egg is useful for drug discovery and development, aiding in lead optimization and improving pharmacokinetics.