Compound Interest Calculator
Project wealth accumulation with lump sums, monthly investing, contribution step-ups, fee drag, and real return analysis for long-horizon planning.
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Inputs
Investment assumptions
Use the core assumptions for a quick projection, or switch on advanced mode to layer in fees, contribution growth, and real-value analysis.
Advanced mode
Add contribution growth, net fee drag, contribution timing, and inflation-adjusted purchasing power.
Compounding frequency
Future value
LKR 2,630,425.58
Total invested
LKR 1,300,000.00
Growth earned
LKR 1,330,425.58
Average annualized outcome
12.00%
Projection
Wealth accumulation curve
Principal, contributions, and compounding gains are stacked to show what is actually driving the terminal value.
Yearly view
How the portfolio builds year by year
Use the table when you need an auditable path from contributions to terminal value.
| Year | Contributed | Growth | Total |
|---|---|---|---|
| 1 | LKR 220,000.00 | LKR 19,507.53 | LKR 239,507.53 |
| 2 | LKR 340,000.00 | LKR 56,708.11 | LKR 396,708.11 |
| 3 | LKR 460,000.00 | LKR 113,845.66 | LKR 573,845.66 |
| 4 | LKR 580,000.00 | LKR 193,448.69 | LKR 773,448.69 |
| 5 | LKR 700,000.00 | LKR 298,366.37 | LKR 998,366.37 |
| 6 | LKR 820,000.00 | LKR 431,809.24 | LKR 1,251,809.24 |
| 7 | LKR 940,000.00 | LKR 597,395.02 | LKR 1,537,395.02 |
| 8 | LKR 1,060,000.00 | LKR 799,200.22 | LKR 1,859,200.22 |
| 9 | LKR 1,180,000.00 | LKR 1,041,818.37 | LKR 2,221,818.37 |
| 10 | LKR 1,300,000.00 | LKR 1,330,425.58 | LKR 2,630,425.58 |
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Perspective
Compounding is powerful, but assumptions matter
The difference between a casual projection and a professional one is usually not the math. It is the assumptions: when contributions happen, how quickly they increase, what fees take away, and what inflation does to future purchasing power.
A plan can look excellent in nominal rupees while being much less impressive in real terms. That is why advanced mode exposes both nominal and inflation-adjusted outputs.
For long-horizon plans, even a seemingly small annual fee can create a surprisingly large drag. This tool surfaces that friction explicitly instead of hiding it inside the final value.
FAQ
Common questions
Why show both nominal and real future value?
Nominal value is the projected rupee amount in the future. Real value adjusts that number for inflation, which better reflects what the money may actually buy.
What is contribution step-up?
Contribution step-up means increasing your monthly investment amount every year. It is a realistic way to model salary growth and usually matters more than trying to time the market.
How does fee drag affect long-term compounding?
Annual fees reduce the net rate applied to your balance every year. Over long horizons, that reduction compounds, which is why even a modest fee can remove a large amount of terminal wealth.
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