Asteroid
The dwarf planet Ceres is by far the largest asteroid, with a diameter of . The next largest are 4 Vesta and 2 Pallas, both with diameters of just over . Vesta is the only main-belt asteroid that can, on occasion, be visible to the naked eye. On some rare occasions, a near-Earth asteroid may briefly become visible without technical aid; see 99942 Apophis.
Near-Earth object
As of January 4, 2019 and mostly using the crude estimate from an absolute magnitude, 897 NEAs listed by CNEOS, including 156 PHAs, measure at least 1 km in diameter, and 8,452 known NEAs are larger than 140 m in diameter.
The smallest known near-Earth asteroid is with an absolute magnitude of 33.2, corresponding to a diameter of about . The largest such object is 1036 Ganymed, with an absolute magnitude of 9.45 and a diameter of about .