As a Christian woman, dressing has always been a challenge to me. The bible uses the word modesty but then sometimes peoples definition of modesty varies. as christians we all want to please God in all we do including our dressing. so we would want to be sure the jeans isn't too tight, the top too revealing or the dress too short. pleasing God doesn't mean you have to look bad or unfashionable, I believe but how can we be sure we're being "modest". this issue is constantly under debate in my youth church. any ideas?
Modesty varies and is largely dependent on motivations. If you're wearing something it shouldn't be so that people will notice you. There's nothing wrong with thinking you look good in an outfit but if you're wearing an outfit so people will notice you or different parts of your body, then that's being immodest.
Other than that, some guiding principals that everyone (men and women) should follow are to make sure nothing sexual is exposed. A lot of people seem to think it's cool to have pants slipping down so that part of one's rear is exposed. That is immodest. A woman doesn't need to have the top button of a blouse always buttoned but neither should she have a plunging neckline. And if she finds that she's intentionally unbuttoning a blouse or wearing something slightly low cut because she want's people to notice her breasts, than that's immodest. Likewise, a man shouldn't walk around in public with his shirt off. It's one thing when it's at home or at a friend's house, but in stores, shops, or on the street? I'd say that's immodest.
As for what's too short, that's going to be cultural and situational, as well as dependent on motivations. For me, I usually keep skirts and shorts mid-thigh or longer. If it's a professional environment or at church, I'd go knee-length or longer. However, I think mid-thigh's the shortest a skirt should be. Any shorter and other body parts might be exposed.
Too tight...I don't think anything should cling to your body, outlining every curve. Clothing doesn't need to be baggy, but it should leave something to the imagination.
Now, all that being said, those are my opinions. The Bible never gives exact cut-off points, which is why I say a lot of it is guided by what motivates people to wear things and the situation (ex. I'd never say it was immodest to wear a bathing suit to the beach even though they show more skin than would be proper in other situations). I think in church, it's best to err on the side of caution.