Year-by-year breakdown
| Year | Contributions | Interest | Balance |
|---|
Assumes contributions at the end of each month and a constant rate. Results are estimates for education only, not financial advice.
What this compound interest calculator does
This calculator shows how much your money could grow when interest is added to your balance and then earns interest itself. Enter a starting amount, how much you plan to add each month, an interest rate and a number of years. You will instantly see your final balance, how much of it came from your own deposits, and how much came from interest.
It works for savings accounts, fixed deposits, index fund investing, retirement planning or any situation where returns are reinvested rather than spent.
How to use it
- Currency: pick the currency you save in. This only changes the symbol, not the maths.
- Starting amount: the money you have today. Enter 0 if you are starting from scratch.
- Monthly contribution: how much you will add each month. Enter 0 to see a one-off deposit grow on its own.
- Annual interest rate: the yearly rate or expected return, for example 4% for a savings account or 7% as a long-term stock market assumption.
- Years: how long the money stays invested.
- Compounding: how often interest is added to your balance. Check your bank or fund documents. Monthly is the most common for savings accounts.
Open Year-by-year breakdown to see your balance at the end of every year.
The compound interest formula
For a single deposit, the standard formula is:
A = P × (1 + r/n)^(n × t)
- A = the final amount
- P = the starting amount (principal)
- r = the annual interest rate as a decimal (7% = 0.07)
- n = the number of times interest is compounded per year
- t = the number of years
When you also add money every month, each deposit grows for the time it remains invested. The calculator works through every month one by one, adds your contribution at the end of each month, and applies interest at the rate that matches your chosen compounding frequency. That is why it can handle any combination of deposits and compounding.
Worked example
Say you start with $10,000, add $200 a month, and earn 7% a year compounded monthly for 10 years.
- Total you put in: $34,000 ($10,000 plus 120 monthly deposits of $200)
- Interest earned: $20,714
- Final balance: $54,714
Now leave everything the same but stay invested for 30 years instead of 10. You put in $82,000 and the balance grows to about $325,159, of which roughly $243,159 is interest. Time does most of the work: in the later years, interest earned each year is larger than everything you deposit.
Does compounding frequency matter?
A little, but less than most people expect. Using the same example over 10 years:
- Compounded yearly: about $53,882
- Compounded monthly: about $54,714
- Compounded daily: about $54,791
The rate you earn, how much you contribute and how long you stay invested matter far more than how often interest is added.
Tips to make compounding work for you
- Start early. Each extra year lets your earlier interest earn interest of its own.
- Automate contributions. A fixed monthly transfer on payday is easier to stick to than deciding each month.
- Watch fees. A 1% yearly fee reduces your rate from, say, 7% to 6%, and that gap compounds too.
- Reinvest returns. Withdrawing interest or dividends stops it from compounding.
Frequently asked questions
What is the difference between simple and compound interest?
Simple interest is paid only on your original deposit. Compound interest is paid on your deposit plus any interest already added, so your balance grows faster over time.
What interest rate should I use?
Use the rate your bank or account actually pays for savings. For long-term investing, many people test a range, such as 4%, 6% and 8%, to see best and worst cases. Investment returns are never guaranteed and can be negative in some years.
What is the rule of 72?
It is a quick way to estimate how long money takes to double: divide 72 by the yearly rate. At 6%, money roughly doubles in 12 years. At 9%, in about 8 years. It is an approximation, not an exact figure.
Does this calculator include inflation or tax?
No. Results are shown before inflation and tax. To see what your future balance might be worth in today’s money, reduce the rate by your expected inflation rate.
Is my data saved?
No. The calculator runs entirely in your browser and nothing you type is stored or sent anywhere.
Related calculators
- Savings goal calculator: find the monthly amount needed to reach a target
- Loan & EMI calculator: see the other side of interest, when you are the one paying it
- All free money calculators
This calculator is for education and planning only and is not financial advice. Actual returns depend on your account, fees, taxes and market conditions.