[2] It has a longer-than average rotation period of 46.30 hours and measures approximately 12 kilometers (7.5 miles) in diameter.

[15] It has also been grouped into the Augusta family by Vincenzo Zappalà in a previous study in the 1990s, also using the hierarchical clustering method.

[15]: 23 In August 2013, a rotational lightcurve of Grubba was obtained from photometric observations by Andrea Ferrero at the Bigmuskie Observatory (B88) in Italy.

Lightcurve analysis gave a longer than average rotation period of 46.30 hours with a brightness variation of 0.24 magnitude (U=3).

[7][8][9] The Collaborative Asteroid Lightcurve Link adopts an albedo of 0.133,[13] and derives a diameter of 14.64 kilometers based on an absolute magnitude of 11.98.