... Just think of a protractor at like 140 degrees. ...
Are talking about the inside angle between the legs of the bend. If so, bend angle is measured by angle through which the conduit is bent. To end up with 140 degrees between legs after bent, you'd bend the conduit to 40 degrees... the complement to 140 degrees, i.e. 180 - 140 = 40.
Many hand benders have marks for 30 and 45 degree bends, some 60. You can generally hit about 40 degrees just by bending a tad short of 45. If you want to be more accurate, get a magnetic digital or protractor level (round with flat or square base, and a degree pointer which relies on gravity to indicate angle).
Bend handle up with conduit flat on floor with level magnetically attached to conduit stub end. Assuming the floor is flat, and because of the bender hook holds the conduit up a little, it may not read 0 at start. Your start will actually be the angle of the floor inline with the shoe. As you bend the conduit, you just take it to whatever degree of bend you want, reading the level's angle as you proceed. You have to go a little past the angle you want due to spring back, then measure angle after relaxing tension on the bender handle.
If there is not enough stub to attach the level, you can attach to bender handle. Hand benders are made so their handles are 60 or 45 degrees in advance of the stub, i.e. straight up when the bend is either 30 or 45 degrees respectively (I refer to them in this respect; in my experience, Gardner Bender benders are the only ones that are 45 degrees). Using this method, you just have to add 60 or 45 degrees to the bend angle you want... although some levels' readout change direction after plumb. For example, a level goes to 90 at plumb then back down to zero on the other side. To make a 40 degree bend with level attached to 30 degree handle, you'd take your bend past 90 to 80 (after relaxing tension on handle and floor is level).
