These data include egg diameter estimates from Grass Carp (Ctenopharyngodon idella) eggs collected during bongo net sampling in the Huron River (Ohio; 41.3305, -82.5812) on May 23, 2022 near Milan, Ohio. Egg diameters were estimated from photographs using proportional relationships of pixel lengths with a known length scale bar in millimeters. Given that eggs were not perfectly spherical, egg diameters were measured across two perpendicular axes and an average was calculated to represent an estimate of egg diameter (mm).