Abstract: Eratosthenes (276 – 194 BC) is the Hellenistic scientist known for calculating the earth’s circumference by using the shadow of a sundial. Today, he is commended for getting admirably close to the currently accepted value for the earth’s circumference. In this paper, I examine Eratosthenes’ experiment through the lens of integrated history and philosophy of science. By using a complementary scientific approach, I point out the conceptual difficulties involved in the instruments and measurements available to him at the time, and argue that his experiment did not warrant the degree of accuracy he is commended for. I suggest that Eratosthenes’ apparent accuracy should be interpreted not as a scientific feat, but as the lucky result of experimental error.