Compound Interest Calculator – See How Money Grows Over Time
Final amount
20,096.61
10,096.61
Interest earned
About Compound Interest Calculator
Enter a starting amount, an interest rate and a time period, choose how often interest compounds, and see the final balance and how much of it is interest rather than your original money.
Compound interest means earning interest on interest already earned. Over short periods the difference from simple interest is small; over decades it is the single biggest factor in how much money you end up with. Seeing the split between what you put in and what the interest added is usually more persuasive than any explanation of the formula.
Compounding frequency matters too, though less than people expect. Moving from annual to monthly compounding at the same nominal rate raises the return slightly; moving from monthly to daily barely moves it at all. The rate and the number of years do the heavy lifting.
What you can use it for
- Project what a savings account or fixed deposit will be worth at maturity.
- See what a long-term investment could grow to at an assumed rate of return.
- Compare two accounts that quote the same rate but compound at different frequencies.
- Show the effect of leaving money invested for another five or ten years.
- Work out how much of a projected balance is your own money and how much is growth.
How it works, step by step
- 1
Enter the starting amount
The principal you are investing or depositing.
- 2
Enter the annual interest rate
The nominal annual rate, before compounding is applied.
- 3
Set the time period
How many years the money stays invested.
- 4
Choose the compounding frequency
Annual, semi-annual, quarterly, monthly or daily. The final amount and the interest earned update immediately.
Frequently asked questions
What is the compound interest formula?
A = P(1 + r/n)^(nt), where P is the principal, r is the annual rate as a decimal, n is the number of compounding periods per year, and t is the number of years.
How is compound interest different from simple interest?
Simple interest is always calculated on the original amount. Compound interest is calculated on the original amount plus all interest already added, so the balance grows faster and faster over time.
Does compounding frequency make a big difference?
Less than most people assume. At the same nominal rate, monthly compounding beats annual by a modest margin, and daily beats monthly by very little. The rate and the length of time matter far more.
Does this account for regular contributions?
No — it calculates growth on a single starting amount. Adding a fixed sum every month would produce a higher result than shown here.
Does it account for inflation or tax?
No. The result is a nominal figure before tax and before inflation, both of which reduce what the money is actually worth later.