Model SIPs, lumpsums, inflation and withdrawals — see what your portfolio actually buys in tomorrow's money.
About this planner
Corpus is a free, browser-based investment calculator built for serious planners. Model a monthly SIP or lumpsum, apply expected returns and inflation, layer in withdrawals, and see what your portfolio actually buys in tomorrow's money — not just a headline nominal figure that inflation will quietly eat.
Everything runs locally in your browser. Nothing is sent to a server. Saved scenarios stay on your device, and shareable links encode the entire scenario into the URL itself.
What it handles
- SIP with annual step-up — model salary growth without maths gymnastics
- Goal-seek mode — enter a target corpus, get the required monthly investment
- SWP sustainability — find out how many years a corpus lasts at a given withdrawal rate
- Two-phase planning — contribute for N years, then withdraw for M years, in one model
- Monte Carlo bands — P10 / P50 / P90 outcome ranges based on return volatility
- Historical backtesting — see how your plan would have performed against Nifty 50 (2000–2024)
- Capital gains tax — optional exit tax with configurable rate and exemption
- Multi-asset allocation — blend equity, debt and gold with per-asset returns
- Scenario comparison — save version A, tweak to version B, overlay on one chart
- Export to CSV and PDF — take your numbers offline
How to use it
For accumulation planning
Pick Accumulate mode. Enter your monthly SIP, expected annual return, inflation, and time horizon. If you expect your salary to grow, set an annual step-up percentage. The final-value tile shows what the corpus will be worth nominally; the second tile shows its purchasing power in today's rupees.
For retirement or FIRE planning
Use Withdraw mode to test whether a corpus can sustain your lifestyle, or Accumulate mode with the two-phase withdrawal option to model contributing until retirement, then drawing down. Check the Monte Carlo tab to see the range of realistic outcomes — not just the average case.
For goal-based planning
Switch to Goal-seek mode. Enter how much you want to end with and when; the planner solves for the monthly SIP required. Useful for house down-payment, child's education, or target-corpus FIRE.
Frequently asked questions
What does this investment calculator do?
Corpus models how money grows or depletes over time given a monthly SIP, lumpsum, expected return, inflation, and optional withdrawals. It shows both nominal final value and real value adjusted for inflation, plus Monte Carlo probability bands and historical backtesting against Nifty 50.
How does inflation adjustment work?
Real value equals nominal value divided by (1 + inflation rate) raised to the number of years. If you end with ₹1 crore after 20 years at 6% inflation, that buys what ₹31 lakh buys today. The inflation-indexed withdrawal option also increases your monthly withdrawal each year by the inflation rate so your purchasing power stays flat.
What is step-up SIP and why does it matter?
Step-up SIP increases your monthly investment each year by a fixed percentage, typically matching your expected salary growth. A ₹25,000 SIP with 10% annual step-up becomes ₹27,500 in year 2, ₹30,250 in year 3, and so on. Over 20+ years, a step-up SIP produces dramatically more corpus than a flat one with the same starting amount.
How accurate is the Monte Carlo simulation?
Corpus runs 800 simulations using a normal distribution around your expected return with the volatility you specify. The P10–P90 band shows roughly 80% of likely outcomes. Real markets have fat tails and sequence-of-returns risk that this simulation understates — treat the band as indicative, not a guarantee.
Can I use this for retirement planning?
Yes. The Withdraw mode takes a starting corpus and a monthly withdrawal amount and tells you how many years the money lasts, with optional inflation indexing. You can also use the two-phase setup in Accumulate mode to model contributing until retirement, then withdrawing afterward, all in one scenario.
Is my data saved anywhere?
No. Everything runs in your browser. Saved scenarios use localStorage on your device. Shareable links encode the scenario into the URL hash itself — nothing is uploaded to any server, and no cookies, analytics or tracking is used.
What return rate should I assume?
Long-term Indian equity has delivered roughly 12% CAGR, debt around 6–8%, gold 8–10%. A balanced equity-heavy portfolio typically models reasonably at 10–12%. For inflation, 6% is a reasonable long-term India assumption. These are planning inputs, not forecasts — use the sensitivity panel to stress-test at ±3%.
Does this handle tax on capital gains?
Optionally. Enable the tax toggle in advanced settings to apply a configurable exit tax on gains above an exemption. Defaults reflect Indian equity LTCG (12.5% above ₹1.25 lakh), but you can adjust for your jurisdiction or asset class.
Can I embed this on another website?
Yes. Append ?embed=1 to any URL to hide the header, footer and navigation, leaving just the calculator. Drop it in an iframe on your own site. Theming is controlled by CSS custom properties, so white-labelling is a one-file edit.
A note on limits
Corpus is a planning tool, not financial advice. Returns are user inputs, not predictions. The Nifty backtest uses price-only returns, not total-return-index figures — actual index-fund performance would typically be 1–2% higher per year due to dividends. Taxes vary by jurisdiction and holding period; always validate numbers with a qualified advisor before making material decisions.