Which service will you likely use?
An uberX car can pick you up in ~11 min.
Distance between Horsham and Gatwick South Terminal is approx. 11.95 miles (19.23 km) with 22 min travel time.
This Uber estimate from Horsham to Gatwick South Terminal
106 days ago.
Update the estimate to see the real-time fare prices with Uber in Horsham.