Q. How do we know that we are dressing with sufficient modesty, especially for Mass ?
A. Common sense, informed by virtue and piety, should guide us in how we dress for Mass. You will find very little in Church documents that spell out how the faithful should dress for Mass other than just one passing comment in the GIRM, which suggests “dignified clothing” for laypeople who carry out any kind of ministerial function at Mass (see No. 339).
I think it is well within the scope of prudence to suggest that Christ’s faithful attend Mass in “dignified clothing.” The exact meaning of that phrase will vary by culture, climate, season and occasion. When it comes to modesty — and this is not only for Mass — I have come up with the following criteria for people: dress in such a way that when friends and strangers approach you their eyes are drawn to look you in the face. In other words, if our manner of dress causes others’ eyes to wander to the wrong places, we are probably immodest.