Open-source investment planning & simulation
Decisions compound too.
Model SIPs, lump sums, contribution pauses, withdrawals, tax-aware cash flows, portfolio rebalancing, historical paths, Monte Carlo scenarios and financial goals - then understand why different investment journeys end differently.
What you can model
Investment Journey Simulator represents a plan as a sequence of contributions and life events rather than a single monthly payment entered into a compound-interest formula.
Monthly compounding on the simulator's stated convention, FIFO lot accounting, two expense-ratio models and multi-fund portfolios. The engine tracks when money enters, what it owns and what happens to each lot over time.
SIPs, lump sums, step-ups, contribution pauses, resumes, systematic withdrawals, depletion, full exits, later restarts and portfolio rebalancing. A plan does not have to remain a straight line for thirty years.
Nominal and inflation-adjusted values, XIRR, post-tax XIRR, goal seek for contribution, return or horizon, drawdown, contribution-versus-growth views and a validation layer that exposes the assumptions behind the result.
Historical replay, rolling backtests, return-path analysis, drawdowns, sequence-of-returns risk, stochastic scenarios, Monte Carlo simulation and block-bootstrap paths sourced from real historical observations.
Compare plans side by side, isolate timing effects and attribute a multi-decision outcome gap to its causes. Shapley-based attribution handles interacting changes so the explained parts add back to the total difference.
Model target allocations, drift, overweight handling, proportion-based rebalancing and alternative rebalancing policies, then compare what those policies actually change in the investment path.
The global engine does not assume a country. For the supported Indian resident-individual scope, the simulator adds lot-level capital-gains treatment, short- and long-term holding periods, the annual exemption, grandfathering, loss set-off and expiry, surcharge slabs, marginal relief, exit load and STT.
A clickable event rail, live Gantt-style journey view, date-aware events, visible units, choose-or-type controls and one shared scenario that carries across the simulator instead of making the user re-enter the same plan on every screen.
Accessible chart colours, scenario persistence, PDF, Excel and JSON exports, reports, source documentation and explicit validation and limitation records. The working is meant to be questioned, reproduced and checked.
Why timing matters
Two plans can invest the same total amount, take the same five-year break, and still finish far apart because the break happened at a different point in the journey.
Trust the working, not the interface
The project documents both what has been tested and what remains a limitation. Numerical output is cross-checked independently rather than relying only on the implementation's own unit tests.
Questions
No. You provide assumptions such as expected return, inflation and contributions. The simulator calculates what those assumptions imply. It does not claim to predict future market returns.
No. SIP and systematic investment plan modelling is one capability. The simulator also handles lump sums, pauses, withdrawals, contribution changes, portfolio rebalancing, goals, historical replay, Monte Carlo scenarios, XIRR and other journey-level decisions.
No. The core investment, contribution, portfolio and simulation engine is designed around general investment journeys. India-specific depth is provided where relevant, including supported resident-individual capital-gains modelling and educational investment guides.
No. Investment Journey Simulator is an educational and simulation tool. Returns are assumptions, tax rules can change, and individual circumstances may require professional advice.
Investment Journey Simulator
Open source, inspectable and designed to make long-term investment decisions easier to reason about without pretending uncertainty does not exist.