for inline spinners i go by the size like a inline spinner that is 2-3 inches overall length including hooks is what i like for river smallmouths and river whitebass also for some small to big pike and i also like some inlines close to 4 inches for fishing in rivers but i go by the length but what about the size in oz? when i buy these i got to the store and look at the lure length not the weight so if im buying online how do i tell the length of the lure from the lure weights. they only offer the sizes in weights (oz) so i cant tell what to get online this can also be said with buying sinkers and weights plus buying blades for making inline spinners if i plan on doing it also hooks. so try your best to explain all of this to me please and thank you

I've ran into this too with other baits.  Two things I have found helpful is that if you look in the catalogs they often will provide details like weight, length, dive depth that they don't on line or on packaging.  the other thing you can do is go to the manufactures website.  Sometimes they'll have the "specs" for each bait available listed.

Also in the catalogs they will often have a chart/graphic that shows the approximate size of of different number hooks/blades/split rings, etc.

Most people buy spinners per their weight  and type of blade they want , usually the heavier the spinner bait the larger it is except with tungueston spinner baits which are smaller in size but has more weight.