Orbital Speed: 27,600Km/h
Orbital Period: 92.68 minutes or 1.5447 hours
So if the ISS is travelling at 27,600KPH and it takes 1.5447 hours to complete an single orbit, then the circumference of the ISS orbit is 42,633.72 Km.
https://www.nasa.gov International Space Station Facts and Figures | NASA
International Space Station Size & Mass. Pressurized Module Length: 218 feet along the major axis (67 meters) Truss Length: 310 feet (94 meters) Solar Array Length: 239 feet across both longitudinally aligned arrays (73 meters) Mass: 925,335 pounds (419,725 kilograms) Habitable Volume: 13,696 cubic feet (388 cubic meters) not including visiting .
Due to orbital perturbations, and atmospheric drag along with periodic orbital boosts, the circumference will vary a bit, but it’ll always be close to post 2.