What were the most popular lengths for baby names in 2014?
For girl names, the top length was 6 letters:

Of all the baby girls accounted for on the SSA’s 2014 baby name list, 28.37% were given a 6-letter name. Though it’s hard to tell by the graph, 2nd place was 5 letters (20.55%) and 3rd place was 7 letters (20.25%).
For boy names, the top length was also 6 letters:

Of all the baby boys accounted for on the SSA’s 2014 list, 29.83% were given a 6-letter name. Next was 5 letters (26.88%), then 7 letters (16.69%).
Unsurprisingly, the top length for all baby names (girls and boys combined) was again 6 letters:

Of all the babies accounted for on the SSA’s 2014 list, 29.13% were given a 6-letter name. Followed, of course, by 5 letters (23.83%) and 7 letters (18.41%).
(We saw the same 6-5-7 pattern for all three groups in 2013 as well.)
U.S. Baby Names 2014: Most popular names, Top girl-name debuts, Top boy-name debuts, Biggest girl-name changes, Biggest boy-name changes, Top first letters, Top lengths