There are 1.609344 kilometers in a mile. It is because as agreed internationally in 1959, length of one foot is defined as 30.48 cm in metric system and there are 5280 feet in 1 mile, that makes 30.48 5280 = 160934.4 centimeters in a mile.

There are 100 000 (one hundred thousand) cm in one kilometer (1 meter is 100 cm and 1 km is 1000 meters, 100 1000 = 100 000 cm in 1 km), then if you divide 160934.4 by 100000, that makes 160934.4 / 100000 = 1.609344 km in a mile. For example, to calculate how many kilometers there are in a mile and a half, multiply the mile value by the conversion factor, 1.5 mi 1.609344 = 2.4 kilometers in a mile and a half.