Compare Compounding and Monthly Contributions

Separate the two sources of growth

The principal is money present at the beginning. A monthly contribution is new money added later. A larger future value can come from either more deposits or more interest, so compare total invested alongside the projection.

Verify the lump sum first

With an assumed ₹1,00,000 principal, 8% annual interest, ten years and yearly compounding, the lump sum grows to approximately ₹2,15,892.50. Set the monthly addition to zero when reproducing that result.

Then use a zero-rate case to check deposits: ₹1,00,000 initially plus ₹1,000 a month for two years gives ₹1,24,000, including ₹24,000 of new contributions and no interest. This arithmetic baseline helps catch mistaken terms or an accidentally repeated principal.

Understand the contribution convention

The principal follows the selected yearly, half-yearly, quarterly or monthly frequency. The optional additions are modeled separately at an annual rate divided by twelve, with deposits at the end of each month. Changing the frequency therefore affects the principal component; it does not change the monthly-addition formula into a yearly contribution schedule.

For clarity, use whole-month periods when including monthly additions. The mathematical expression can accept fractional periods, but it does not model a bank’s actual daily ledger or a real sequence of contribution dates.

1. Check principal growth with additions set to zero.
2. Add an affordable monthly amount and record total invested.
3. Change one assumption at a time.
4. Keep the assumed rate and timing convention with the copied balance.

Interpret projections cautiously

A constant return is a scenario, not a promise about investments. Fees, tax, inflation and market volatility are outside the calculation. The interface’s nonnegative assumptions do not describe the full possibility of investment losses.

The CFPB explanation of compound interest describes interest on accumulated interest. For beginning-of-month investment contributions, compare SIP Calculator, whose deposit timing differs from this tool’s optional monthly additions.