Sizing question

So im looking to buy my first pair of redwings, and was trying to figure out what size to get and saw that the website had a thing where it tells you your size by photo, so I did that and the measurements it gave me were accurate but it told me my size is a 4.5(mens) but in every other brand of shoe/boot im a size 8.5, is the size the website gave me accurate? Any advice is appreciated :)