driftcurve vs Flexible Retirement Planner

driftcurve is an open-source household retirement planning engine for projecting finances and comparing retirement outcomes. It can model multiple household members, account types, debts, mortgages, pensions, Social Security and property sales. Its default Monte Carlo simulations resample annual market data from 1966–2024 across equities, Treasuries, residential real estate, inflation and Bitcoin. Users can adjust historical returns toward their own long-run targets or enter static annual assumptions. Risk-based spending guardrails solve for monthly spending and suggest adjustments based on portfolio thresholds and probability of success. A Compare page puts two scenarios on one chart. In default local mode, household data and saved scenarios stay in browser localStorage, while forecasts run through a Python backend; there is no account or server-side database persistence. Optional multi-user mode adds email/password accounts, server-side sessions, and stored profiles and scenarios. The project offers forecast and guardrails API endpoints, plus authentication, profile and scenario endpoints in multi-user mode. It is free under Apache License 2.0. The maker describes it as an educational modeling tool, not licensed financial, investment, tax or legal advice.

Flexible Retirement Planner models retirement outcomes with Monte Carlo simulation and reports the probability that a plan succeeds. It runs 10,000 simulated paths spanning savings accumulation and retirement spending. Users can compare Stable, Flexible, and Conservative spending policies, test different assumptions, and use sensitivity analysis to see which inputs affect results most. The standalone version lets users save inputs and maintain multiple what-if scenarios, and it works offline. The planner includes income and savings growth projections, withdrawal planning, detailed tax modeling, and Social Security modeling. Standalone downloads are provided for Windows and Mac/Linux; the Windows version does not require Java. The planner is free for individual non-commercial use, and educators and trainers may use it for educational purposes. A voluntary contribution of any amount unlocks a personal-use license key. Commercial use, including by financial planners, is not authorized or supported. Its maker, Random Walk Ventures LLC, created it in 2006.