I am 15 years old and run a 4.8 40yd dash.
As a 100 yard dash sprinter in the 60's the average time would be about 10.2 to 10.3.
It is average.
The average 40 yard dash speed for an CB in the NFL is 4.25 to 4.45
Im sorry to say its not when i was in middle school we had big guys who could run it in a 5'6 to a 5'0 flat
40 yard dash/10 yard dash= 4 What ever the time you got for the ten yard, you multiple it by 4. It could be an average of your running time per 10 yard dash. Sometimes for several runners, they would feel worn out by the time when reaching the 40 yard mark.