TOMS shoe's and size's.?

So im buying my first pair of TOMS and you can only get them online.. i normally dont buy shoes online but i really want some TOMS. I was wondering how to pick sizes.. i wouldnt want to buy them and when they get here.. be to small. I wear a size 71/2 in my " sperry top siders. Should i just get an 8 in TOMS.? HELP! :)