250-750 µm
Amoeba proteus is a large protozoan, and it can grow up to 1 mm long (average size 250-750 µm). The size ranges based on the amount of food it engulfs. It can almost be seen with the naked eye (still very difficult due to its colorless and transparent body).

Extended read:

Facts about Amoeba
This article covers
- What is Amoeba?
- Is Amoeba a cell?
- What is inside Amoebas’ “false feet” or “pseudopods”?
- How does Amoeba proteus eat?
- What is Amoeba proteus’ favorite food?
- Tell me more about the secrets of Amoeba proteus!
- How big is the Amoeba proteus ?
- How fast the Amoeba proteus can move?
- Does Amoeba proteus have eyes?
- How does Amoeba proteus breathe?
- How does Amoeba proteus reproduce?
- Where to look for Amoeba proteus?
- How to find Amoeba proteus under an optical microscope?
- What to look for under the microscope?
- I saw some shiny particles inside Amoeba proteus. What is that?
- Do other Amoebas also look like Amoeba proteus?
- Where did the name “Amoeba” come from?
- How is Amoeba classified?
- I heard that Amoebas can eat human brains. Is it true?