What is the approximate circumference of Earth at the equator?

The approximate circumference of Earth at the equator is 40,075 km.

Earth is not a perfect sphere: it bulges slightly around its middle because of rotation. Using the standard equatorial radius of about 6,378.137 km, geodesists calculate the equatorial circumference as approximately 40,075.017 km. That is why quiz answers usually round it to 40,075 km.

This measurement differs from the circumference measured through the poles, called the meridional circumference, which is about 40,008 km. The equatorial value is larger because the planet's rotational bulge adds roughly 67 km to the route around the middle.

A common mix-up is confusing circumference with diameter. Earth's equatorial diameter is about 12,756 km, while 40,075 km is the distance around the planet. The equator is also the longest circle of latitude and lies at 0 degrees latitude.