Glossary
Every term Vundii uses, in plain English. Deep-dive links point to the full concept pages.
Monte Carlo simulation
Running your retirement thousands of times (Vundii uses 6,000) with randomized market returns based on historical behavior, instead of assuming one fixed future. The spread of outcomes is what produces your success rate. Full concept →
Success rate
The percentage of simulated retirements in which your savings lasted through your planning horizon. 85%+ is generally strong; below 70% warrants attention. A "failure" means spending would have needed to adjust, not a cliff. Full concept →
RMD (Required Minimum Distribution)
After age 73, the IRS requires annual withdrawals from traditional (pre-tax) accounts like 401k and IRA, taxed as ordinary income — whether you need the money or not. Full concept →
IRMAA (Income-Related Monthly Adjustment Amount)
A Medicare surcharge for higher-income retirees. Cross an income threshold — even by one dollar — and your Part B and D premiums increase significantly for the year. Often triggered by large RMDs or Roth conversions.
Roth conversion
Moving money from a pre-tax account (traditional IRA/401k) into a Roth. You pay income tax on the converted amount now; all future growth and withdrawals are tax-free, with no RMDs ever. Full concept →
Roth Optimizer
Vundii's tool that plans annual conversions sized to fill your current tax bracket without spilling into the next — and reports whether the strategy beats doing nothing for your specific numbers.
Equity %
The share of an account invested in stocks; the rest sits in bonds. More equity means more growth potential and bigger short-term swings. Vundii lets you set it per account.
Inflation rate (per expense)
How fast a specific expense grows each year. At 3%, a $1,000/month cost becomes $1,344 in 10 years and $1,806 in 20. Healthcare typically runs 5–6%; a fixed mortgage payment runs 0%. Full concept →
Guyton-Klinger guardrails
An adaptive withdrawal strategy: trim spending when the portfolio falls behind, allow more when it runs ahead. Small flexible adjustments dramatically improve survival odds versus rigid withdrawals. Full concept →
Sequence-of-returns risk
The danger of poor market returns early in retirement. Withdrawing from a portfolio during an early crash sells shares at the bottom — damage that later recoveries can't fully repair. Full concept →
Withdrawal order
The sequence you draw from account types in retirement. The common default — taxable first, then traditional, then Roth — minimizes lifetime taxes for many (not all) situations. Full concept →
Safe withdrawal rate
The annual percentage of your portfolio you can withdraw with high odds of never running out. The classic guideline is 4% of the starting balance, inflation-adjusted — a sanity check that simulation then personalizes.
FRA (Full Retirement Age)
The age you receive exactly 100% of your Social Security benefit — 67 for anyone born in 1960 or later. Claiming earlier permanently reduces the check; later permanently increases it. Full concept →
PIA (Primary Insurance Amount)
Your base monthly Social Security benefit, calculated from your highest 35 earning years. Claiming at FRA pays 100% of PIA; other ages adjust up or down. Your real number lives at ssa.gov. Full concept →
Break-even age
The age at which total lifetime benefits from claiming Social Security later overtake claiming earlier — typically 78–82. Live past it and waiting paid off. Full concept →
Stress test
Replaying history's worst market openings — 2008, the 1970s stagflation, the dot-com bust — against your plan to see whether it survives. Full concept →
Inflation sensitivity grid
A table showing how your success rate changes across combinations of inflation rates and market-return assumptions — revealing how sensitive your plan is to each.
Glide path
Gradually shifting your portfolio from stocks toward bonds as retirement approaches, reducing exposure in the years when sequence risk is highest. Full concept →
Bracket creep
When RMDs and other income push you into higher tax brackets in later retirement — often accompanied by IRMAA surcharges and more of your Social Security becoming taxable. Full concept →
See these ideas working on your own numbers.
Try it in Vundii →