Trying to figure out my target for financial independence and is about to start building an investment portfolio for 3 lifetimes. (3 lifetimes as in I want to inherit it to my kids and grandchildren: 80 x 3 = 240 years horizon).

I'm looking for help to figure out my Financial independence (FI) target. I have been to the subreddit of said subject and found this thread here: [https://money.stackexchange.com/questions/69993/](https://money.stackexchange.com/questions/69993/how-to-calculate-years-until-financial-independence)

* I have also used this calculator: [Networthify](https://networthify.com/calculator/earlyretirement?income=50000&initialBalance=0&expenses=20000&annualPct=5&withdrawalRate=4)
* I have also used the formula from the wiki (see above answer)

I want to **figure out my FI target** and **years to FI** in my own calculations. I record all my income and expenses every month and I have made an excel sheet to update this as time goes by. 

Here are some relevant figures: 

* Age: 28 y/o
* Annual income: $31,000 after tax
* Annual expenses: $21,000
* Portfolio: $10,000 (zero tax on all financial investments)
* SWR (withdrawal rate): 4%
* Nationality: Non-US (401k etc. does not apply to me)
* ROI: 4%
* Savings rate: 32%
* Multiple: 25

Here is a quote by a money.stack user that uses some parameters I've found everywhere on the web (also from the Trinity study).

> 
> Which in turn means that I estimate I need investments 1/.04 times the
>  yearly spending estimate to declare the "forever"
>  independence/retirement, or 25x the yearly. @Keshlam
> 
> 
> 

I have also visited the Monevator, a blog that recommended this process:

```
http://monevator.com/financial-independence-plan/#footnote_2_24108

```

1. Annual income / Withdrawal rate = FI target
2. Take FI target
3. monthly saving figure
4. real return rate assumption
5. Feed numbers into calculator
6. = Years until you are FI!

Here are my calculations so far:

```
FI target using 4% SWR: annual expenses / SWR = FI: 21000/0.04=$525,000

FI target using multiple of 25: annual expenses * multiple = FI: 21000*25=$525,000

FI target using annual income and SWR: annual income / SWR= FI: 31000/0.04=$775,000

Years to FI using wiki formula: ((21000/0.04)-10000)/(31000*0.32)= 51.5 Years

```

Perhaps I am overcomplicating things, but I want this to work as I track the expenses on a rolling 12 month period and regularly watch my savings rate. Basically, I don't know if I can trust my calculations to be "fair". (they will never be the truth, I get that).