Retirement Calculator Walkthrough: Social Security + 401(k) + IRA Together
Estimating retirement income gets complicated because three separate streams converge at different ages. Social Security earliest at 62 (with permanent reduction), full retirement age 67 for those born after 1960, and delayed credits up to age 70. 401(k) and IRA withdrawals can start penalty-free at 59½, with Required Minimum Distributions kicking in at 73 under SECURE 2.0. Here's how to layer them in a calculator.
Step 1 — Get your Social Security estimate from ssa.gov
Log into your my Social Security account at ssa.gov for your personalized benefit estimates at age 62, FRA (typically 67), and 70. The 2026 average benefit is roughly $1,950/month for retired workers, but high earners with 35 years of maximum-taxable earnings can hit $4,000+/month at FRA.
Claiming at 62 reduces your benefit by 25–30% permanently. Delaying past FRA earns 8% per year up to age 70 — a guaranteed return that's hard to beat anywhere else. Married couples should also model survivor benefit strategy, often delaying the higher-earning spouse.
Step 2 — Project 401(k) and IRA balances at retirement
Use the calculator's compound growth feature with realistic assumptions: 7% nominal return for a 60/40 portfolio (per Vanguard's 10-year capital market expectations) and 2.5% inflation. Contribute current annual amounts plus expected increases.
Example: $300,000 balance at age 50, contributing $24,000/year (2026 employee limit), at 7% nominal returns reaches roughly $1.04M at age 65. Add Social Security and you have a clearer income picture.
Step 3 — Apply the 4% safe withdrawal rate (and its caveats)
The Trinity Study and Bengen's 1994 paper found that 4% inflation-adjusted withdrawals from a 60/40 portfolio survived 30-year retirements in 95%+ of historical periods. $1M portfolio = $40,000 safe annual income, indexed to inflation.
Modern updates (Wade Pfau, Michael Kitces) suggest 3.0–3.5% may be safer for current bond yields, with potential to flex up via the "Guyton-Klinger guardrails" approach. Add Social Security on top: $40K SWR + $30K Social Security at FRA = $70K gross retirement income, before state taxes and Medicare premiums.
Frequently asked questions
What if I want to retire before 59½?
Two main options: Rule of 55 (penalty-free 401(k) withdrawals if you leave the employer at age 55+ for that specific 401(k)), or 72(t) Substantially Equal Periodic Payments (SEPP) for IRA withdrawals at any age, computed via IRS-approved formulas. Both have strict rules — work with a CPA.
How does Medicare factor in?
Medicare Part A is free at 65 if you've paid Medicare tax 40+ quarters. Parts B and D run $185+/month for higher-income retirees (IRMAA brackets), and a Medigap or Medicare Advantage plan adds $100–$300/month. Budget $400–$700/month per person for Medicare-related costs in retirement.
What about Roth conversions before RMDs hit?
The window between retirement (say age 60) and RMD age (73) is often the optimal Roth conversion period — low income, time for tax-free compounding, and reduces future RMD burden. Run scenarios in the calculator with conversion amounts of $20K–$80K/year through that window.