Investment Calculator

What this calculator actually models

This investment calculator projects the future value of a portfolio built from two ingredients: a one-time initial investment and a fixed monthly contribution, both compounding at your expected annual return. It answers the single most useful question in personal investing: if I keep doing what I'm doing, where do I end up?

The projection uses monthly compounding, which mirrors how most real-world investments accrue. Each month, your entire balance grows by one-twelfth of the annual rate, and then your new contribution is added on top. Over long horizons this ordering matters: money invested earlier spends more months compounding, which is why the first years of contributions do disproportionate work in the final number.

The formula behind the numbers

The future value combines two standard formulas. The lump sum grows as FV = P × (1 + r/12)^12t, while the stream of monthly contributions grows as an annuity: FV = C × [((1 + r/12)^12t − 1) / (r/12)], where P is your initial investment, C the monthly contribution, r the annual return, and t the number of years. The calculator sums both, month by month, so the yearly table you see is exact rather than an approximation.

A useful mental shortcut is the Rule of 72: divide 72 by your annual return to estimate how many years your money takes to double. At 12%, that's roughly six years — meaning a 24-year horizon gives your earliest money four doublings, or sixteen times its original value.

The three levers, ranked by what they cost you

Every projection here is driven by three inputs, and they are not equal. Time is the strongest and cheapest lever: starting five years earlier routinely beats contributing 50% more, because early money occupies the longest stretch of the compounding curve. Contribution is the lever you control most directly — and unlike returns, every extra rupee is guaranteed to show up in the outcome. Return is the weakest lever to chase: moving from 10% to 12% requires taking on real additional risk, while moving your start date or SIP amount requires only a decision. A practical exercise: fix your return assumption, then use the calculator to find the contribution that makes your goal work — not the return that makes your current contribution look sufficient.

Choosing a realistic return assumption

The single biggest source of error in investment projections is an optimistic return input. Long-run equity returns have historically averaged 10–12% in India (Nifty 50, pre-tax) and 7–10% in the US (S&P 500, nominal), but returns arrive unevenly — a 12% average can include −20% years. For planning, many advisors model equity at 10–12%, hybrid portfolios at 8–10%, and debt-heavy portfolios at 6–7%. If your goal is critical (a child's education, a house down payment), run the calculator a second time at a rate 2–3 points lower and plan around the more conservative number.

Also remember this calculator shows nominal value. At 6% inflation, ₹30 lakh in 15 years buys what roughly ₹12.5 lakh buys today. For inflation-adjusted planning, pair this tool with our inflation impact calculator or use the SIP calculator's real-returns toggle.

Reading the yearly projection table

The table under the chart repays close reading. Watch for the crossover year — the first year in which investment growth exceeds your annual contributions. Before it, you're doing the heavy lifting; after it, the portfolio is. On typical inputs (8–12% returns with steady monthly investing) this lands between years 8 and 12, and it's the psychological milestone that makes staying invested easier: from there on, a market dip of a few percent can wipe out a whole year of contributions on paper — which feels alarming but is precisely the sign the machine has scale. Investors who understand the crossover in advance panic less when volatility finally shows up in rupee terms rather than percentages.

Common mistakes this calculator helps you avoid

• Waiting for a "better time" to start. Delaying a 15-year plan by three years typically costs more than a quarter of the final corpus — time in the market beats timing the market for regular contributors.
• Ignoring contribution growth. Most people's incomes rise; most projections don't. If you expect to increase contributions annually, the step-up SIP calculator models that far more accurately.
• Comparing pre-tax projections to post-tax goals. Long-term capital gains tax (12.5% above ₹1.25 lakh per year in India; 0–20% in the US depending on bracket) will reduce the corpus you can actually spend.
• Treating the projection as a promise. It's a trajectory under constant assumptions — revisit it yearly and adjust contributions when reality diverges.

When to use this tool versus its siblings

Use this calculator for a quick lump-sum-plus-monthly projection in any currency. If you invest through Indian mutual funds and want step-up contributions, scenario comparison, or inflation adjustment, the SIP calculator is the deeper tool. If you're planning backwards from a target amount ("how much must I save monthly to reach X?"), the savings goal calculator inverts the math. And if you're weighing investing against paying off debt, the payoff-vs-invest calculator compares both paths side by side.