Clock method to convert miles to kilometers

Use the clock method to estimate conversion between mph and km/h.

Example: 45 mi in km

• 45 mi == 45 minutes on the clock
• 45 minutes is 75% of the clock
• so 45 mi is around 75 km

To convert back, divide by 2 and add everything except for ones place:

• 130 km. digits 1,3,0
• 130/2 = 65
• 65 + 13 = 78 mi
• so 130 km is around 78 mi