Getting comfortable with kilometers per hour

In many tennis matches, serve speeds are measured in kilometers per hour.  For those of you who, like myself, do not yet have a good feel for the metric system and are not sure how fast a serve really is when it's measured in kph, I provide below a conversion table to mph:

Mph                                                    Kph

100                                                     161

110                                                     177

115                                                     185

120                                                     193

125                                                     201

130                                                     209

135                                                     217

140                                                     225

145                                                     233

150                                                     241

How is serve speed measured?

Serve speed is measured by radar guns located on the backdrops behind the servers (one at each end) and they measure the speed of the first strong signal they detect.  Thus the speed of the ball is measured just as it leaves the racquet.  The ball quickly slows down due to air resistance etc.  The wide serve reads at slower speeds because the speed gun has a less direct line of sight to the ball.  Wide serves are not measured as accurately as those that go down the middle.