The formula with 26.2 substituted
miles = 26.2 ÷ 1.609344 = 16.280
The constant is an exact definition, not a rounded factor: the mile is 1.609344 km, the US gallon is 3.785411784 litres and the imperial gallon is 4.54609 litres. The Kilometres to Miles Converter explains where each comes from and gives a longer table.
At a walking pace of 5 km/h, 26.2 km takes about 314 minutes. At an easy running pace of 10 km/h it takes about 157. In metres it is 26,200.
What 26.2 kilometres means in practice
26.2 km is 16.28 miles, and most people who search it have the marathon in mind with the units crossed: the marathon is 26.2 miles, which is 42.2 km. As a kilometre distance, 26.2 km is a long training run of about two and a half hours.