The calculated distance (air line) between Sai Ying Pun and Dongguan is approximately 56 miles respectively 90 kilometers.
By car or train, the actual journey to Dongguan is certainly longer, as only the direct route (as the crow flies) between Sai Ying Pun and Dongguan has been calculated here.
Air line (approximately)
90 kilometers
49 nautical miles