We work out a suggested amount to feed per day based on your pet's age, weight and activity level. As an example, for an adult dog that has an average activity level and wants to maintain current weight, we would recommend they feed approximately 2% of bodyweight per day.
Check out our suggested Feeding Amounts for both cats and dogs.
Remember, though, every pet is different. Monitor their condition closely, and adjust their intake as needed (and let us know if you need help with this too!)