Fitting length
（重定向自Nilpotent length）
![Combining the lower Fitting series and lower central series on a solvable group yields a series with coarse and fine divisions, like the coarse and fine marks on a ruler.](/Images/godic/202501/29/Steel_ruler_closeup2732.jpg")
In mathematics, especially in the area of algebra known as group theory, the Fitting length (or nilpotent length) measures how far a solvable group is from being nilpotent. The concept is named after Hans Fitting, due to his investigations of nilpotent normal subgroups.