How much do you want to have saved in your 401/IRA for retirement?  

Lots of questions first. 1) are you debt free? 2) If not, how long will it take you to get there? 3) How much do you have now? 4) Any other sources of income?

I have a retirement from a previous career so my investments can remain untouched. My first advise is to get a professional financial advisor. They will guide your finances and maximize your investments. This is so critical in the ups and downs that occur. Further, stats show that those who use a professional will earn 4-8 percent more than those that go it alone. Great return for about 1.18% fee.

If you have minimal debt, you could do it with a million using the 4% rule and still grow your money. In my example, I started with about 600K when I started using a financial advisor. 7 years later it is nearly 2M and remains untouched. I'll draw SS next year and will start pulling a few percent from investments. 

You can do it. Be smart. Get rid of debt and save. Good luck.