The calculated distance (air line) between Katwijk aan den Rijn and Zoetermeer is approximately 10 miles respectively 16 kilometers.
By car or train, the actual journey to Zoetermeer is certainly longer, as only the direct route (as the crow flies) between Katwijk aan den Rijn and Zoetermeer has been calculated here.
Air line (approximately)
16 kilometers
9 nautical miles