Compound Interest Calculator
Calculate compound interest and total accumulation with dedicated Month Mode (% per month, monthly compounding) and Year Mode (% per annum, annual compounding). Save customer records, track compounding periods, and export history.
Calculation Details
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Fill in the principal, interest rate, and duration on the left, then click Calculate Interest to see compound interest growth and breakdown.
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Compounding in Month Mode vs. Year Mode
Compounding represents the addition of interest to the principal sum of a loan or deposit, or in other words, interest on interest:
- Month Mode (Monthly Compounding): The entered rate is applied per month, and interest is calculated and added to the principal balance at the end of each month. In informal/community financing, ₹10,000 at 5% per month compounded for 12 months produces ₹7,958.56 in interest (Total: ₹17,958.56).
- Year Mode (Annual Compounding): Common in formal banking and long-term deposits where interest is added once per year. ₹10,000 at 5% per annum for 1 year produces ₹500 in interest (Total: ₹10,500).
Formulas & Compounding Rules
Both modes follow standard exponential financial mathematics:
- Final Total Amount (A):
A = P × (1 + R/100)^T - Compound Interest (CI):
CI = A − P - P (Principal): The initial amount invested or borrowed.
- R (Rate of Interest): Periodic interest rate (% per month in Month Mode; % per year in Year Mode).
- T (Periods): Total number of compounding cycles (months or years).
Why does Month Mode produce higher returns than Year Mode?
In Month Mode, interest is calculated and added to your balance 12 times in a single year, causing subsequent months to generate interest on all previously accumulated interest. In Year Mode, interest is added only once per year.
Is my financial data or customer details stored on a remote server?
No. Utility Seva operates with strict 100% in-browser client-side privacy. Calculations and history records are preserved only on your device using localStorage. No information is transmitted to external servers.
Can I enter fractional rates and decimal durations?
Yes. You can enter decimal amounts for principal (e.g. ₹15,450.50), interest rates (e.g. 2.75%), and fractional periods.