The time it takes for a frog to lay eggs and then to have those eggs hatch depends on the type of frog, but the average length of time for the hatching of eggs is between 6 to 21 days after fertilization, as reported by Hamline University. Many frogs are able to lay their eggs immediately after fertilization takes place.
The American Bullfrog can lay up to 20,000 eggs at a single time. These frogs live between 7 and 9 years, and they are the largest of the frogs in North America. These frogs have larger females than males and are found in most of the freshwater areas in North America, including lakes, ponds and marshes.
Most frogs will breed in the spring and all frogs will follow the growth pattern of eggs to tadpoles to froglets and then to frog. Once the frogs have fertilized their eggs, laid the eggs and watched the eggs hatch, then the tadpoles arrive. Tadpoles spend most of their early days hiding inside of the grassy weeds, but will begin to swim after a period of approximately 7 to 10 days. They will then spend several weeks growing arms and legs while their tail begins to disappear. From here, the tadpoles will turn into froglets and then will turn into frogs.