1 Mile equals 1.609344 Kilometer.
Also, if your speedometer is strictly in Kilometers Per Hour,
the same number is used. Here's some values for the more common
speeds.
35 mph - 56.3 kh
55 mph - 88.5 kh
60 mph - 96.6 kh
65 mph - 104.6 kh
70 mph - 112.7 kh
75 mph - 120.7 kh
Enjoy!