There are guidelines for Catholic women with regard to modest clothing.
Essentially, it involves keeping to the standards of modesty that were the norm for Catholic women up until the twentieth century.
As well as the length, women need to make sure that skirts (and also other clothing) are not "figure-hugging".
In other words, the clothing should not highlight the woman's figure, but should obscure the woman's figure.
Alls this is explained in a very clear way in the link which I provided on another thread.
I advise women to print this out and take it with them when they are shopping for clothes.
Here it is again:
This link provides information for Catholic women who want to know how to dress properly:
http://www.salvemariaregina.info/Modesty.html 1. "Marylike" means modesty without compromise -- "like Mary," Christ's pure and spotless Mother.
2. Marylike dresses have sleeves extending to the wrists; and skirts reaching the ankles.
3. Marylike dresses require full and loose coverage for the bodice, chest, shoulders, and back; the cut-out about the neck must not exceed "two fingers breadth under the pit of the throat" and a similar breadth around the back of the neck.
4. Marylike dresses also do not admit as modest coverage transparent fabrics -- laces, nets, organdy, nylons, etc. -- unless sufficient backing is added. Fabrics such as laces, nets, organdy may be moderately used as trimmings only.
5. Marylike dresses avoid the improper use of flesh-colored fabrics.
6. Marylike dresses conceal rather than reveal the figure of the wearer; they do not emphasize, unduly, parts of the body.
7. Marylike dresses provide full coverage, even after jacket, cape or stole are removed.
8. Marylike fashions are designed to conceal as much of the body as possible, rather than reveal. This would automatically eliminate such fashions as slacks, jeans, shorts, culottes, tight sweaters, sheer blouses, and sleeveless dresses; etc. The Marylike standards are a guide to instil a "sense of modesty." A girl or woman who follows these, and looks up to Mary as her ideal and model, will have no problem with modesty in dress. She will not be an occasion of sin or source of embarrassment or shame to others. The standard set by the Cardinal Vicar of Pope Pius XI (quoted above) is meant to delineate between "decent" and indecent; it would be sinful to wear clothes which "cannot be called decent." We expect that members of the Fatima Crusade, who are resolved to make reparation for the sins of the world -- especially of immodest and impurity, will do far more than the minimum. They will truly strive to imitate the Blessed Virgin Mary in the virtue of modesty. Keep this guide with you when buying clothes. Make sure that you purchase or make only garments which meet the Marylike Standards.
"Be Marylike by being modest -- be modest by being Marylike."
There are places where you can buy entirely modest, yet also nice looking clothes.
I intend to post a list of these places on CathInfo.