DAX function

PERCENTILE.INC — DAX function reference

Percentile of a column.

Syntax

dax

PERCENTILE.INC(<column>, <k>)

dax

PERCENTILE.INC(Sales[Amount], 0.9)

→ A number

dax

PERCENTILE.INC(Sales[Amount], 0.5)

→ The 50th percentile — equivalent to MEDIAN for this column

dax

CALCULATE(PERCENTILE.INC(Sales[Amount], 0.25), Sales[Region] = "West")

→ 25th-percentile (lower quartile) order value in the West region

PERCENTILE.INC is inclusive of the 0 and 1 endpoints (k=0 returns the minimum, k=1 the maximum); PERCENTILE.EXC excludes the extremes and requires k strictly within a narrower range — using EXC on a small dataset can return an error where INC would not.
Like MEDIAN, it’s a non-additive statistic — you can’t sum or simply combine percentile values computed at a finer grain to get the percentile at a coarser grain; it must be recalculated at whatever grain you display it.

From Math & statistics