The following notes on wand length are taken from notes on the subject by Mr Garrick Ollivander, wandmaker:
Most wands will be in the range of between nine and fourteen inches. While I have sold extremely short wands (eight inches and under) and very long wands (over fifteen inches), these are exceptionally rare. In the latter case, a physical peculiarity demanded the excessive wand length. However, abnormally short wands usually select those in whose character something is lacking, rather than because they are physically undersized (many small witches and wizards are chosen by longer wands). .