Thought I'd throw this out to the community.

In most circumstances, if one is looking to FI on $1M, then the first $500K will take quite a bit longer than the second $500K because while saving for the second $500K, the first $500K is generating its own green soldiers. This means while $500K is the halfway FI point in raw numbers, when one reaches $500K, it will be well past the expected halfway point in time to FI.

I'm looking for a tool where one could input monthly savings and expected return to determine when time-related benchmarks are reached.

For example, if one is looking to be FI on $1M, saves $3K/month in a tax-advantaged account, and expects a 7% return, then it will take roughly 16 years to reach $1M from $0.

With the same assumptions, that individual would be at roughly $380K (38%) at 8 years, the halfway point in time between starting at $0 and reaching FI. So that individual would be expected to be "halfway there" in time at $380K, or 38% of the FI number.

Similarly, that person would be 1/4 of the way to FI in time at $165K and 3/4 of the way to FI in time at $664K.

While my math skills are only sufficient enough to use a retirement calculator with nice round numbers to figure this out, is anyone aware of a tool or formula where one could easily change the inputs (amount saved/month, expected return, etc.) and receive a breakdown of raw dollar amounts that are roughly associated with time to FI so I could put my numbers in and see that I will be 1/4, 1/2, 3/4 to FI in time at $x saved?

I understand this would be a pretty pointless tool, but may be fun to play around with. It could also be motivating to reach certain time benchmarks that are not the typical round numbers of having, say 100K saved. Nothing wrong with having more numbers to celebrate (cost-consciously of course) while trekking through the long monotonous climb to FI!