
It all comes down to interest rates. As an investor, all you’re doing is putting up a lump-sump payment for a future cash flow. – Ray Dalio
“Interest” is interesting, understanding this in personal finance or investment term will make you wealthy or poverty-sicken. Sadly most people only focus on borrowing on lower interest rate but never pay attention to how they can grow money and build wealth.
Interest is calculated based on interest rate
What is Interest Rate?
Interest rate is ‘returns you earn on your investment‘ or ‘the cost of borrowing on your debt‘ For the savers and investors it is the money in amount earned on investment or savings (principle amount) and for borrowers it’s the money on principle amount (fee or rent) you pay to the lender on the debt.
Calculating Interest
Interest can be calculated in two ways: simple interest or compound interest.
Simple interest
Simple interest is the interest calculated on the principle money lend or borrowed. The Formula to calculate is Principal x Interest Rate Per Year x Term (years).
Usually simple interest are used for calculating interest amount for short term debt or savings like certain types of bonds, certificates of deposit (CDs), savings accounts, treasury bills, personal loans, student loans, and auto loans, payday loans, car title loans and more.
For Example. if you borrow or lend 1000 dollars to or from bank or with a interest rate of 10% and agreed to pay off in 3 years You will earn or pay $1000 x (10/100) x 3. = $90 interest amount. So at the end of the 3 years you will earn or payed $1090. i.e. Principle + interest amount = $1000 + $90 = $1090.
Compound interest (interest on interest)
Compound interest (interest on interest) is the interest calculated on the initial principle amount that is lent or borrowed. The beauty of compound interest is that income or debt is calculated from accumulated interest earned or owed from previous periods Formula to calculate compound interest is = Principal x [(1 + Annual Interest Rate/100)^(Number of Compounding Periods) – 1] ^ = power of. Formula seems to be complicated. US investor.gov site has as calculator which is very easy to use.
Usually compound interest are used for calculating interest amount for long term debt or savings like certain types of bonds, certificates of deposit (CDs), savings accounts, treasury bills, mortgage.
For example: if you borrow or lend 1000 dollars to or from bank or with a interest rate of 10% and agreed to pay off in 3 years You will earn or pay $1000 x [(1 + (10/100)) ^ (36 ,months)] = $331.18 interest amount. So at the end of the 3 years you will earn or payed $1090. i.e. Principle + interest amount = $1000 + $331.18 = $1331.18.
If you are a saver or lender compound interest will make your money grow at an accelerating rate over time, sadly if you are a borrower your debt will grow in accelerating rate over time.
Below are the 3 key factor you should keep in mind when you lend or borrow money.
- Interest Rate: The higher the interest rate, faster you income or debt will grow.
- Compounding Frequency: The smaller the compounding frequency, your will money or debt will grow exponentially. for example every day, month or year.
- Time or Duration: The longer the better as interest on interest will grow your income or debt faster.
NOTE: The beauty of compounding is you accelerate wealth exponentially. You build wealth by combining the 3 key factor to your advantage. For borrower you path to poverty will be accelerate exponentially.
Compound Vs. Simple Interest
Comparing our example between Simple Interest $90 and Compound Interest $348.18 compound interest gets us 2.86 time more interest money to be earned or owed.

Compound Interest will accelerate the building of wealth for lenders and savers on flip side it also accelerate borrowers to poverty if they don’t have ability to pay their debt
Disclaimer –
“Believe nothing, no matter where you read it, no matter if I have said it, unless it agrees with your own reason and common sense.” – Buddha
