Solve gaping necklines and tight armholes with a custom-fit paper pattern and one dart tweak.
A standard-size blouse is drafted for an average that almost nobody actually is. The two complaints we hear most are a neckline that gapes and an armhole that binds, and both come from the same cause: the pattern was graded up or down as a whole, rather than drafted from a real upper chest measurement.
Upper chest is the measurement that governs a blouse. Take it high, straight across the chest above the bust and under the arms, with the tape flat. Everything else — shoulder finishing, sleeve round, the front dart point — follows from it proportionally. That is why our form asks for upper chest first and only then opens the other fields.
If your neckline gapes, the usual fix is not to cut the neck smaller. It is to move the front dart point closer to the true bust point, which pulls the fabric into the dart instead of letting it fall away at the neck. A quarter of an inch changes the whole line.