The calculated distance (air line) between Najafgarh and Karol Bāgh is approximately 13 miles respectively 21 kilometers.
By car or train, the actual journey to Karol Bāgh is certainly longer, as only the direct route (as the crow flies) between Najafgarh and Karol Bāgh has been calculated here.
Air line (approximately)
21 kilometers
11 nautical miles