Formula Help

[catprog]

I am trying to find/calculate the formulae for the following and I was wondering if anyone could offer help:

Given desired number of years working, income , interest rate and current savings, how much do I need to save now to achieve the goal.

[Goldielocks]

Game changer:

https://www.mrmoneymustache.com/2012/01/13/the-shockingly-simple-math-behind-early-retirement/

[Freedomin5]

Your inputs don’t matter if you don’t have expected FIRE expenses. Once you know your expected expenses you can very easily figure out how much you need to save.

[Zette]

If you are making a spreadsheet, the function you want is called PMT.  Just plug in your retirement goal as the “loan” amount. Your current savings are the present value (pv).

https://www.wallstreetphysician.com/financial-calculations-payment-pmt-function/

How to use the Excel PMT function | Exceljet
https://exceljet.net › excel-functions › excel-pmt-function
The Excel PMT function is a financial function that returns the periodic payment for a loan. You can use the NPER function to figure out payments for a loan, given the loan amount, number of periods, and interest rate. rate - The interest rate for the loan. nper - The total number of payments for the loan.


Also useful are future value, present value, and NPER.

https://exceljet.net › excel-functions › excel-fv-function
Excel FV Function. Summary. Get the future value of an investment. future value. =FV (rate, nper, pmt, [pv], [type]) rate - The interest rate per period. The future value (FV) function calculates the future value of an investment assuming periodic, constant payments with a constant interest rate.

[BTDretire]

I am trying to find/calculate the formulae for the following and I was wondering if anyone could offer help:

Given desired number of years working, income , interest rate and current savings, how much do I need to save now to achieve the goal.

 How would I go at it? Say you need $50k for your living expenses. That would mean you need $1,250,000
if you follow the 4% rule. Say you now have $250,000 and you can save $30k per year.
Using this calculator, http://www.moneychimp.com/calculator/compound_interest_calculator.htm
I put in the following numbers;
Current Principal  $250,000
Annual addition  $30,000
Years to grow  11.2   I adjusted this number until the Future Value was $1,250,000
Interest Rate  9%   Pick your own number.
Compound Interest (4) times annually
And the Future Value is $1,260,130
 Now you can adjust any of the values and then lastly the 'Years to Grow' to get the Future Value you want.
 The downside and I rarely see this mentioned is in 11.2 years with inflation at 3% the buying power of $1,250,000 is down to about $900,000.
You will need 1,750,000 to have the buying power of $1,250,000 if inflation is 3% over the next 11.2 years.
 I really like that MoneyChimp calculator and use it forward or often will reiterate to back into a number.

[wageslave23]

I am trying to find/calculate the formulae for the following and I was wondering if anyone could offer help:

Given desired number of years working, income , interest rate and current savings, how much do I need to save now to achieve the goal.

 How would I go at it? Say you need $50k for your living expenses. That would mean you need $1,250,000
if you follow the 4% rule. Say you now have $250,000 and you can save $30k per year.
Using this calculator, http://www.moneychimp.com/calculator/compound_interest_calculator.htm
I put in the following numbers;
Current Principal  $250,000
Annual addition  $30,000
Years to grow  11.2   I adjusted this number until the Future Value was $1,250,000
Interest Rate  9%   Pick your own number.
Compound Interest (4) times annually
And the Future Value is $1,260,130
 Now you can adjust any of the values and then lastly the 'Years to Grow' to get the Future Value you want.
 The downside and I rarely see this mentioned is in 11.2 years with inflation at 3% the buying power of $1,250,000 is down to about $900,000.
You will need 1,750,000 to have the buying power of $1,250,000 if inflation is 3% over the next 11.2 years.
 I really like that MoneyChimp calculator and use it forward or often will reiterate to back into a number.

To correct for that issue, I usually adjust my rate of return by inflation.  So if I think the market will return 7%, then I use 5% to adjust for inflation.

[BTDretire]

I am trying to find/calculate the formulae for the following and I was wondering if anyone could offer help:

Given desired number of years working, income , interest rate and current savings, how much do I need to save now to achieve the goal.

 How would I go at it? Say you need $50k for your living expenses. That would mean you need $1,250,000
if you follow the 4% rule. Say you now have $250,000 and you can save $30k per year.
Using this calculator, http://www.moneychimp.com/calculator/compound_interest_calculator.htm
I put in the following numbers;
Current Principal  $250,000
Annual addition  $30,000
Years to grow  11.2   I adjusted this number until the Future Value was $1,250,000
Interest Rate  9%   Pick your own number.
Compound Interest (4) times annually
And the Future Value is $1,260,130
 Now you can adjust any of the values and then lastly the 'Years to Grow' to get the Future Value you want.
 The downside and I rarely see this mentioned is in 11.2 years with inflation at 3% the buying power of $1,250,000 is down to about $900,000.
You will need 1,750,000 to have the buying power of $1,250,000 if inflation is 3% over the next 11.2 years.
 I really like that MoneyChimp calculator and use it forward or often will reiterate to back into a number.

To correct for that issue, I usually adjust my rate of return by inflation.  So if I think the market will return 7%, then I use 5% to adjust for inflation.

 That will certainly work, but you still don't know what your FIRE number is. That's why I use the MoneyChimp calculator and put the FIRE number I calculate in today's dollars into 'Current Principal' then put my inflation number in 'Interest Rate' and the number of years until retirement in the 'Years to Grow', to then find the future retirement date FIRE Number under 'Future Value'.
I do understand that is a little bit scarier number to look at.

[RWD]

Try playing around with this calculator:
https://networthify.com/calculator/earlyretirement

[catprog]

Try playing around with this calculator:
https://networthify.com/calculator/earlyretirement

It is almost the same it is just the other way around then what I am looking for.

I am also trying to do it over many different end points so I can look at it at the end of year and see how I am going.