Nobita is ten years old.
This information is directly from the provided reference: "Nobi Nobita, a ten-year-old boy and the central character of the cartoon, is an utter mediocrity or less in everything he does."
The reference clearly states Nobita's age as ten years old. He is the main protagonist of the Doraemon series, known for his adventures with his robotic cat friend and his friends Gian, Suneo, and Shizuka.
