When I was younger, working as an employee for large corporations, I used to think that the optimal amount for each person to put into their 401k is the level that maximizes the employer match.
That is wrong. Oh, if I could only teach my younger self what I know now!
If the goal is wealth building, and if the strategy is to increase wealth building while paying the least in taxes, the optimal amount for each person to put into their 401k each year is the maximum amount allowed by law.
In 2019, the maximum amount allowed is $19,000 for each person in the United States, plus an additional $6,000 for anyone over the age of 50. If you aren't putting this much into your 401k, you are paying too much in taxes, and you aren't maximizing the building of your net worth.