Early spring, and a garden pond is suddenly full of grey jelly. Look closely and every clear bead holds a black dot about 1 mm wide. In a few months, some of those dots will be hopping across the lawn.
A frog’s life cycle has four main stages: egg (frogspawn), tadpole, froglet and adult frog. The tadpole lives in water and breathes with gills; during metamorphosis it grows legs and lungs and its tail shrinks away, turning it into a froglet that can live on land. Some guides count three or five stages, and a few frogs skip the tadpole stage altogether.
Key takeaways
- 4 stages: egg → tadpole → froglet → adult. In the common frog, froglets become adults after about four years (University of St Andrews).
- Metamorphosis is the big change from water-breathing tadpole to air-breathing frog. Thyroid hormones control it.
- Not every frog has a tadpole: the Puerto Rican coqui develops completely inside its egg and hatches as a tiny froglet.
What are the 4 stages of the frog life cycle?
The four stages of a frog’s life cycle are egg, tadpole, froglet and adult. Eggs are laid in water as frogspawn. Tadpoles hatch and live underwater, breathing through gills. As they metamorphose they become froglets, with legs and a shrinking tail. Finally they grow into adult frogs, which breed and start the cycle again.
The timeline below follows the common frog (Rana temporaria) of Europe, using the University of St Andrews’ tadpole research pages. Other species follow the same pattern at different speeds.
- Egg (frogspawn). In spring the female lays big clumps of eggs in a pond. Each round black egg is about 1 mm wide, wrapped in a blob of jelly. After a few days the eggs start growing into tiny tadpoles inside the jelly.
- Tadpole. Hatchlings are about 5 mm long and at first can’t swim; they wriggle by bending their bodies. Once the tail is big enough they swim off to feed, breathing with external gills and grazing on pond weed and algae. Later they develop lungs, come up to breathe, and grow back legs.
- Froglet. Front legs appear, the tail shrinks until it has almost gone, and the little froglet climbs out onto land.
- Adult frog. Froglets stay near the pond and grow through the summer, hibernate from autumn to spring, and become adults after about four years. Adults return to water to mate and lay spawn.
Source: University of St Andrews, Tadpoles project.
Is it 3, 4 or 5 stages? Why books disagree
All three answers describe the same life cycle; they just cut it up differently. Three-stage diagrams use egg, tadpole and adult. Four-stage diagrams, the most common in schools, add the froglet. Five-stage diagrams split the tadpole into a young tadpole and a “tadpole with legs”. None is wrong, so use the version your teacher or exam board uses.
| Count | Stages | When it is used |
|---|---|---|
| 3 stages | Egg → tadpole → adult | Simple diagrams for younger pupils |
| 4 stages | Egg → tadpole → froglet → adult | Most school courses and diagrams |
| 5 stages | Egg → tadpole → tadpole with legs → froglet → adult | More detailed diagrams that show metamorphosis step by step |
The froglet deserves its own stage because it is a real in-between form: it has legs and lungs like an adult, but often still has a stub of tail and is far from fully grown.
What happens during metamorphosis?
Metamorphosis is the transformation from tadpole to frog. New body parts appear (legs), larval parts are broken down and absorbed (the tail), and organs such as the skin and gut are remodelled. Thyroid hormones orchestrate these changes, explains a review by Laudet (2011) in Current Biology.
That is why the tail doesn’t drop off. The tadpole’s body absorbs it, reusing the material while the froglet can’t yet feed well. Gills give way to lungs, which is why older tadpoles start swimming up to gulp air.
How long does it take for a frog egg to become a frog?
It depends on the species and the water temperature. Common frog tadpoles usually turn into froglets within one spring and summer. American bullfrog tadpoles can take a few months in the warm south of the USA but up to three years in Michigan and Nova Scotia, says the IUCN’s Global Invasive Species Database.
Bullfrogs show just how much frogs vary: a single bullfrog clutch can hold up to 20,000 eggs, according to the IUCN Global Invasive Species Database. Only a small share of eggs ever become adult frogs, which is why frogs lay so many.
Picture it: from 1 mm to frog
A common frog egg is about 1 mm wide, the size of a full stop on this page, and a new hatchling is about 5 mm long, shorter than a grain of rice. Within a single summer it can turn into a froglet that hops onto land. Then it takes about four more years to grow into a full adult (University of St Andrews).
Egg: 1 mm
Hatchling tadpole: 5 mm
Up to 20,000 eggs in one bullfrog clutch, compared with one tadpole that may survive
Do all frogs have a tadpole stage?
No. Some frogs skip the free-swimming tadpole stage completely. The Puerto Rican coqui tree frog (Eleutherodactylus coqui) develops entirely inside its egg and hatches as a tiny froglet, often with a small tail, says the University of St Andrews. This is called direct development.
Skipping the tadpole means these frogs don’t need a pond to breed, so they can lay eggs on land in damp forests. Other frogs have their own twists: marsupial frogs carry their eggs, which can measure up to 10 mm across, in a pouch on the mother’s back. Read about more survival tricks in frog adaptations.
What do tadpoles and frogs eat?
Young tadpoles graze on pond weed and algae, and older common frog tadpoles need to eat meat as they grow their back legs, says the University of St Andrews. Adult frogs are predators that catch insects and other small animals. So one animal changes from plant-grazer to hunter during its life, which also changes its role in the pond.
Why are frogs important to ecosystems?
Frogs link water and land food webs. Tadpoles graze algae in ponds, adults eat insects on land, and at every stage frogs are food for fish, birds, snakes and mammals. When frogs disappear, those links break. Because frogs live in both worlds, they are sensitive to pollution and disease in either.
That sensitivity is showing. The fungal disease chytridiomycosis has contributed to the decline of at least 501 amphibian species over the past half-century, including 90 presumed extinctions, report Scheele and colleagues (2019) in Science. You can help by building a wildlife pond without fish, never moving frogspawn or tadpoles between ponds (which can spread disease), and never releasing pet frogs into the wild.
Myths about the frog life cycle
Myth: A tadpole’s tail falls off.
Fact: The tail is broken down and absorbed by the body during metamorphosis (Laudet 2011). Why people believe it: the tail seems to vanish quickly, so it looks as if it dropped off.
Myth: All frogs start life as tadpoles.
Fact: Some, like the coqui, hatch straight out of the egg as froglets (University of St Andrews). Why people believe it: the familiar pond frogs of Europe and North America all have tadpoles.
Myth: A frog is fully grown as soon as it leaves the water.
Fact: A froglet is still tiny. Common frogs take about four years to become adults (University of St Andrews). Why people believe it: froglets look like miniature adults.
Test yourself
1. Put the four stages in order.
Egg (frogspawn), tadpole, froglet, adult frog.
2. What happens to a tadpole’s tail?
It shrinks as the body breaks it down and absorbs it.
3. Name a frog that skips the tadpole stage.
The Puerto Rican coqui tree frog.
Where to next?
➡️ Go wider: animal adaptations explained, structural, behavioural and physiological⬆️ Go deeper: frog adaptations🔀 Go sideways: the life cycle of a butterfly, another metamorphosis
Frequently asked questions
What is the life cycle of a frog in short?
Egg, tadpole, froglet, adult. Frogs lay eggs in water; tadpoles hatch, breathe with gills and grow; during metamorphosis they grow legs and lungs and lose their tail to become froglets; froglets grow into adults that return to water to breed.
Is a frog’s life cycle complete or incomplete metamorphosis?
“Complete” and “incomplete” metamorphosis are terms used for insects, not frogs. Frogs simply undergo metamorphosis: a big change from a water-living larva (the tadpole) to an adult that can live on land. Compare it with a butterfly’s life cycle.
How many eggs does a frog lay?
It varies hugely by species. Common frogs lay big clumps of spawn, while a single American bullfrog clutch can contain up to 20,000 eggs, according to the IUCN Global Invasive Species Database. Frogs with direct development, like the coqui, lay far fewer, larger eggs.
Do tadpoles breathe air?
Young tadpoles breathe with gills. As they develop, they grow lungs and swim to the surface to breathe air, while their gills are absorbed, says the University of St Andrews. Adult frogs breathe air with their lungs.
Sources
- University of St Andrews, Tadpoles project. Life cycles.
- Laudet, V. (2011). The origins and evolution of vertebrate metamorphosis. Current Biology 21(18).
- IUCN SSC Invasive Species Specialist Group. Global Invasive Species Database: Lithobates catesbeianus (American bullfrog).
- Scheele, B. C. et al. (2019). Amphibian fungal panzootic causes catastrophic and ongoing loss of biodiversity. Science 363(6434).
Sources checked 12 October 2026.
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