Estimate compound interest growth with optional contributions and inflation adjustment.
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Interest is the compensation paid by a borrower to a lender for the use of money. It is one of the most fundamental concepts behind loans, savings, and investments. This Interest Calculator helps estimate interest earned or paid over time.
There are two primary methods of calculating interest: simple interest and compound interest.
Simple interest is calculated only on the original principal amount. It does not take previously earned interest into account.
Example: Borrowing $100 at 10% interest for one year results in $10 interest. After two years, the total interest becomes $20.
Compound interest is calculated on both the principal and accumulated interest. This means interest is earned on interest, leading to faster growth over time.
Using the same $100 example at 10% interest: after two years, the total amount becomes $121 instead of $120.
The more frequently interest is compounded (monthly, daily, continuously), the greater the final amount will be.
The Rule of 72 is a quick way to estimate how long it takes for money to double at a given interest rate.
For example, at 8% interest, money will double in approximately 9 years.
Fixed interest rates remain constant over the life of the loan or investment. Floating rates change based on benchmark rates such as the Federal Reserve rate or LIBOR.
This Interest Calculator works with fixed interest rates for simplicity and accuracy.
Some investments allow periodic deposits. Contributions made at the beginning of a period earn more interest than those made at the end.
Interest income may be subject to taxes depending on the type of investment. Taxes can significantly reduce the final amount earned over time.
Inflation reduces the purchasing power of money over time. To grow real wealth, interest or investment returns must exceed inflation.
This calculator allows inflation to be excluded for quick estimates or included for more realistic results.
Simple interest is calculated only on the principal, while compound interest includes interest on interest.
Compound interest is far more common in real-world loans and investments.
Inflation reduces real returns, making higher interest rates necessary to grow wealth.
Yes, it follows standard financial formulas used globally.
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