Percentage of Total days in a month till current date

We want to get a percentage of Total days in a month till current date / total days in a month

Eg.

Suppose in April 2018 as per fiscal period(Technical Week) total number of days is 29

Today is April 25 th 2018

So they want to have a kf which will calculate a percentage

KF 3 = 25/29 *100 = 86%

Any idea how to get this done in IBP