What if you run the 100m in 12 seconds what is your mph speed?

Dividing distance travelled by time taken gives 100/12 = 8.5 metres per second.

There are 3600 seconds in one hour, therefore, 8.5 metres per second is equal to 8.5 x 3600 = 30600 metres per hour.

There are 1609.344 metres in one mile. Therefore, rounded to two decimal places, 30600 metres per hour is equal to 30600/1609.344 = 19.01 miles per hour.