How many greek gods and goddesses were there?

There is only ever 12 greek gods/goddesses at one time, however many greek believed in roman gods, but the main 15 greek gods/ goddesses are:

Aphrodite

Apollo

Ares

Artemis

Athena

Demeter

Dionysus

Eros

Hades

Hephaestus

Hera

Hermes

Hestia

Poseidon

Zeus