The formula with 10 substituted
miles = 10 ÷ 1.609344 = 6.214
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, 10 km takes about 120 minutes. At an easy running pace of 10 km/h it takes about 60. In metres it is 10,000.
What 10 kilometres means in practice
10 km is 6.21 miles, the 10K, a standard road race and the point many runners aim for after a 5K. Twenty-five laps of a track, about two hours walking, 50 to 65 minutes for a recreational runner.