The calculated distance (air line) between Russia and Mongolia is approximately 1,015 miles respectively 1,633 kilometers.
By car or train, the actual journey to Mongolia is certainly longer, as only the direct route (as the crow flies) between Russia and Mongolia has been calculated here.
The center of the country is used to calculate the distance. For a more precise determination of the distance, please use one (or better yet two) cities for the distance calculation.
Air line (approximately)
1,633 kilometers 881 nautical miles