Compound interest calculator with regular contributions
Enter a deposit, a rate and a term to see what it grows to, how much of that is interest, and what each year adds, with monthly or yearly contributions if you make them. It is all calculated in your browser, so nothing you enter is sent anywhere.
Year by year
Opening balance, money added, interest earned and closing balance for each year of the term.
| Year | Opening | Contributions | Interest | Closing |
|---|
Compounding frequency at a glance
Your deposit, rate, term and contributions at each frequency. Compounding more often lifts the effective annual rate a little; the gap grows with the rate and the term.
| Compounded | Times a year | Effective rate | Interest | Final amount |
|---|
Questions
Built by Mohd Shayan. Found a problem or have an idea? Send a note.
How is compound interest calculated?
A = P × (1 + r ÷ n)n × t, where P is the starting amount, r the annual rate as a decimal, n how many times a year interest is compounded and t the time in years. ₹1,00,000 at 8% for 10 years compounded yearly is ₹1,00,000 × 1.0810 = ₹2,15,892.50, so ₹1,15,892.50 of interest. Compounded monthly instead, n is 12 and the exponent 120, which gives ₹2,21,964.02.
What does the compounding frequency change?
How soon earned interest starts earning interest of its own. The nominal rate stays the same, but the effective annual rate rises a little with each step: 8% compounded half-yearly is 8.16% a year, quarterly 8.243%, monthly 8.3% and daily 8.328%. Bank fixed deposits in India usually compound quarterly and PPF yearly, so pick the frequency your product uses.
How are regular contributions worked out?
Each contribution is added at the start or the end of its month or year and then grows at the rate for the time left, which is the annuity formula: contribution × ((1 + i)N − 1) ÷ i, where i is the rate per contribution period and N the number of contributions, times (1 + i) when paying at the start. ₹5,000 a month at 12% for 10 years, compounded monthly and paid at the end of each month, grows to ₹11,50,193.45 from ₹6,00,000 put in; paid at the start of each month it reaches ₹11,61,695.38. If interest compounds less often than you contribute, each contribution grows at the equivalent rate for its own months.
What is the difference between compound and simple interest?
Simple interest is paid on the original deposit only: interest = P × r × t, so ₹1,00,000 at 8% for 10 years earns ₹80,000. Compound interest is also paid on the interest already earned, which is why the same deposit earns ₹1,15,892.50 with yearly compounding. The gap starts small and widens every year, so compounding matters most over long terms. The simple interest line in the results gives each contribution simple interest for the time it is invested.
How long does money take to double?
Divide 72 by the rate for a quick estimate: about 9 years at 8%, about 6 at 12%. The exact answer with yearly compounding is log 2 ÷ log(1 + r), which at 8% is 9.006 years: after 9 full years ₹1,00,000 has become ₹1,99,900.46, just short of double. Set the term to 9 years and then 10 to see it cross.
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