Swap fats in recipes without changing results.
Butter is approximately 80% fat, 15% water, and 5% milk solids. Oil is 100% fat. Therefore: 100g oil = 120g butter (add 20% to account for water). Conversely: 100g butter = 83g oil. In baking, butter provides flavor and creates flakier textures (the water creates steam pockets in pastry). Oil makes moister cakes that stay fresh longer because liquid fat coats flour proteins more evenly. Butter has a smoke point of 350°F (175°C), while most cooking oils are 400-500°F. For high-heat sautéing, use oil. For flavor and pastry, use butter. Ghee (clarified butter) is 99.5% fat with a 485°F smoke point — the best of both worlds for cooking.