Script that calculates compound interest on investment
Removed bloat
Claned up a and b functions
cleaned up description of one function


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You can also use your local clone with git send-email.


A python script that calculates compound interest on investments. Calculations are based on these formulas.

#How to use (besides having python3 installed)

Clone and cd into the project folder

git clone https://git.sr.ht/~rickylinden/pengan && cd pengan

Make executable if needed and run the script as

python3 pengan.py

The script will ask you if you want to:

  • a) See how much monthly investment becomes over time

  • b) See how much you need to invest to reach a certain amount of money

Enter the values it asks for, if fields are left empty it runs with example values.

#An example

You put 1000€ into an investment account that on average gives 5% annual interest. Additionally you'll add 100€ per month for 10 years. So if you started in 2021 you should have 16533.24€ in 2031.

$ python3 pengan.py 
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+
|c|o|m|p|o|u|n|d| |i|n|t|e|r|e|s|t| |c|a|l|c|u|l|a|t|o|r|
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+

a) How much does a monthly investment become in x amount of years?
b) How long does it take to get a certain sum by investing?

Choose a or b: a

Starting amount (empty = 0€): 1000
Monthly sum (empty = 500€): 100
Years (empty = 30): 10
Average interest rate (empty = 5%): 5

After 10 years you should in total have: ~16533.24€.
Which means that in the year 2031 you'll get a monthly average of ~68.88€ in interest.

#If you notice an issue

Open up a ticket