what is the difference between iv% and top iv?

Percentage IV is from 1 - 100 percent and top IV's are from 0 - 15.

atk iv. 0-15
def iv 0-15
stamina iv 0-15

simple as that.
websites can give you a percentage which is cool.. ya know. like straight 15s is 100%...

straight 10s is 30/45. 30 because 10 times 3. 45 because 15 times 3 .

the percentage is 66.67% its very very very very very very simple/ the other guy that answered it tells you how simple it is