See what a one-time investment grows into — adjust for inflation, and optionally add a monthly SIP on top to model your real portfolio.
How lumpsum compounding works
A one-time investment grows by the full return on the whole amount, every year, with each year's growth itself earning returns the next year:
Future value = P × (1 + r)years
where P is the amount invested and r the assumed annual return. The longer the period, the more the curve bends upward — the last few years of a 20-year holding typically add more rupees than the first ten.
CAGR — the number that makes returns comparable
CAGR (Compound Annual Growth Rate) is the steady yearly rate implied between a starting and an ending value: CAGR = (FV ÷ P)1/years − 1. Fund factsheets quote it because it strips out the lumpiness of yearly returns. A handy mental shortcut is the rule of 72: money doubles in roughly 72 ÷ return years.
Worked example: ₹1 lakh at 12% for 10 years
₹1,00,000 × (1.12)10 = ₹3,10,585 (₹3.11 lakh) — your money roughly triples. Adjusted for 6% inflation, that future value buys about ₹1,73,429 worth of goods in today's money. That gap is exactly why the inflation toggle exists.
What ₹1 lakh grows into (assumed returns)
| Years | 8% p.a. | 10% p.a. | 12% p.a. |
|---|
| 5 | ₹1,46,933 | ₹1,61,051 | ₹1,76,234 |
| 10 | ₹2,15,892 | ₹2,59,374 | ₹3,10,585 |
| 15 | ₹3,17,217 | ₹4,17,725 | ₹5,47,357 |
| 20 | ₹4,66,096 | ₹6,72,750 | ₹9,64,629 |
Illustrative compounding at assumed constant rates — actual mutual fund returns vary year to year and are not guaranteed.
Lumpsum + SIP: the combo most investors actually run
Real portfolios are rarely either/or. A bonus or FD maturity goes in as a lumpsum while the monthly SIP keeps running. Use the optional SIP field above to model both together — the result panel shows the combined corpus and each component, so you can see what each rupee stream contributes.
Frequently Asked Questions
Lumpsum vs SIP — which is better?
Mathematically, a lumpsum invested in a rising market earns more because the full amount compounds from day one. But a SIP spreads your entry across months, reducing the risk of investing everything at a peak — and it matches how salaries actually arrive. If you already have the money (a bonus, maturity proceeds), a common middle path is a lumpsum plus a continuing SIP; this calculator models exactly that. For SIP-side planning, use our
step-up SIP calculator.
What is CAGR?
Compound Annual Growth Rate — the single steady yearly rate that would take your starting amount to the ending amount. If ₹1 lakh becomes ₹2 lakh in 6 years, the CAGR is about 12.2%, even if the journey was bumpy. It is the right way to compare investments held for different periods.
How does inflation change the picture?
It shrinks what the future value actually buys. ₹1 lakh at an assumed 12% becomes about ₹3,10,585 in 10 years — but at 6% inflation that is worth only about ₹1,73,429 in today's money. Switch the inflation toggle on to see the real figure for your own inputs.
Can I combine a lumpsum with a monthly SIP?
Yes — use the optional "Add monthly SIP" field. It is the most common real-world pattern: invest a bonus or FD maturity as a lumpsum while continuing a monthly SIP. The result shows the combined corpus plus each part separately.
How is a lumpsum mutual fund investment taxed?
On redemption, as capital gains (as of FY 2025-26): equity funds held over 12 months pay 12.5% LTCG above the ₹1.25 lakh annual exemption; held 12 months or less, 20% STCG. Debt funds bought after 1 April 2023 are taxed at your slab rate regardless of holding period. Tax applies only when you redeem, not while it compounds.
What return should I assume?
It is an assumption, not a promise. Planners commonly model 10–12% for diversified equity funds over long periods and 6–7% for high-quality debt — but actual returns vary widely year to year. Run a conservative case (say 10%) alongside an optimistic one before committing to a goal.
How long does it take to double my money?
The rule of 72: divide 72 by the annual return. At 12% a lumpsum doubles in roughly 6 years; at 8%, roughly 9 years. It is an approximation of the exact compounding math this calculator does.
Estimates are for information and education only — not financial, tax or investment advice. Verify current rates and rules with official sources.