Why toe units are confusing
Alignment sheets, forum posts and string-line DIY guides all describe toe differently: degrees or inches, total or per wheel, measured at the tire or the rim. A "1/16 in toe-in" and a "0.15°" setting can be the same thing on one car and different on another, because inches depend on how far apart the measuring points are.
The math
toe (inches) = measurement diameter × tan(toe angle). Use the tire's overall diameter if the measurement was taken at the tread (like most string setups), or the rim diameter if it was taken at the rim lip. Total toe is the sum of both wheels; per wheel is half.
What toe does
Toe-in at the front calms the car down and helps straight-line stability; toe-out sharpens turn-in but makes the car more darty. At the rear, a little toe-in keeps the car stable; rear toe-out is usually a mistake. Toe also wears tires fast when it's off, so it's the first thing to check after lowering a car.