Boiling whole potatoes takes around 35 minutes to 40 minutes.
When boiling potatoes for making mashed potatoes it takes around 15 minutes for chopped up potatoes to boil and soften enough to be mashed.
For whole potatoes it takes around 35 to 40 minutes of boiling the whole potatoes for them to be soft enough to mash the potatoes.
The potatoes will get softer much faster if you cut them up first before boiling them which is what I do.
I always chop up the potatoes into smaller pieces and then place them in the pot, add water and then allow them to boil for 20 minutes.
After 20 minutes of boiling the chopped up potatoes the potatoes are soft enough to be mashed easily.
I use a mashed potato smasher tool that works great at mashing the potatoes.
However you can also use a hand held mixer or even a regular mixer which does a faster job.