To a great extent it depends on the time and circumstances. I believe Paul was basically talking aboutwithin a church meeting or the market place. He did not have the summer beach in mind, where more skin would be exposed due to cooling, tanning, and swimming. And I think he may have been speaking about being in order instead of being flamboyant. Look at 1 Timothy 2:9--
"In like manner also, that women adorn themselves in modest apparel, with shamefacedness and sobriety; not with broided hair, or gold, or pearls, or costly array;" (KJV).
The word "modest" is Strongs number G2887 "Kosimos", meaning "orderly" and or "well arranged". Don't confuse this word with "kosmos" (world). And the word "shamefacedness" is Strongs G127 meaning "a sense of shame and modesty". They are to keep in mind those around them and not be indifferent. Then we also have "sobriety"which is Strongs number 4997, (sophosune), which denotes sober mindedness.
With these parts looked at a little closer the word modest as used here is more about the flashiness of clothing and style. Paul is seemingly suggesting that the ladies dress in such a way as to not stand out. He would have frowned upon the late Carmen Miranda, and her hats and flamboyant outfits. It is the word shamefacedness that is more related to offending others. In otherwords, a lady that does not care if she is upsetting others by being half-naked in church or at the market, or decked out like a Christmas tree, is not really much of a lady at all. People tend to have little respect for someone like that. In the last half of the verse Paul clearly is speaking about elaborate outfits and style. In short, this verse is not so much about bare skin but is more about some people being over fancy and decked out..putting on a show. The word "shamefacedness" would of course apply to other times and places (I suppose), so the young women should not be indifferent to others, including the men, whilst on a beach. They can not just say "I do not care".. That is not a Christian attitude.