RetireRange — Planner’s Guide

Written so a financial professional can evaluate the model behind a RetireRange plan. This guide answers the questions a planner asks when a client brings in a set of results: how the numbers were produced, what assumptions and approximations went into them, how to read the outputs, and where the model is likely too cautious or too rosy. It can get technical.

The three documents

• Methodology — how the engine works, the full assumptions catalog with defaults, the per-topic methodology (returns, withdrawals, taxes, Social Security, RMDs, medical, mortality, Roth, optimizer), how to interpret each result metric, and the built-in cross-checks.
• Model limitations, by portfolio inventory — the limitations mapped to the specific accounts, assets, and income sources a household holds, with a "leans conservative / optimistic" flag on each.
• This index.

Looking for how to actually use the tool rather than how the model works? That’s the Help center — task-oriented walkthroughs of each tab and question, where this guide is the technical model spec behind them.

The 60-second version

RetireRange is a Monte Carlo retirement simulator. For a household’s saved plan it runs 5,000 independent simulations (configurable), each drawing a correlated monthly sequence of asset-class returns and inflation across the full horizon (typically 35–75 years). Each month it applies contributions, computes and allocates withdrawals across account tax types, applies returns, accrues federal + state tax, tracks RMDs and Social Security, handles medical costs, and optionally fires mortality events. It then aggregates the runs into a distribution of outcomes — success rate, percentile ending balances, after-tax legacy, and per-year income/tax/RMD trajectories.

Its purpose is strategy comparison under controlled luck, not point-prediction: named strategies run against shared random seeds, so differences in outcome reflect the strategy rather than the draw. Read every result as a modeled probability, and use the limitations — especially the items that lean optimistic (long-term care, fees, life-insurance drag, un-subtracted taxes) — to calibrate how much weight to put on a given plan.