The Complete Guide to Retirement Planning
Retirement is the single largest financial goal most people will ever have, and it's the goal where small adjustments today produce enormous differences in outcome. The mathematics are unforgiving in both directions: a person who saves 15% of income from age 25 will retire comfortably under almost any scenario, while a person who waits until 45 to start saving 15% will likely have to work into their 70s or accept a meaningfully lower standard of living.
This guide explains how the retirement calculator above works, walks through the assumptions that matter most, and addresses the planning questions that separate adequate retirement preparation from optimal preparation.
Understanding the Inputs
Current age and retirement age together define your accumulation horizon. The traditional retirement age is 65, but Social Security full retirement age has shifted to 67 for anyone born after 1960, and many planners now model to age 70 to maximize Social Security benefits and account for longer life expectancies.
Current savings is the total of all retirement-designated accounts: 401(k), 403(b), 457, traditional IRA, Roth IRA, SEP-IRA, and any taxable brokerage accounts you're earmarking for retirement. Don't include emergency funds, your home equity (unless you plan to downsize), or 529 education accounts.
Monthly contribution is your regular saving rate. The standard recommendation is 15% of gross income including any employer match — a number that will sound aggressive to most people but produces realistic retirement outcomes. If you're starting late, 20% to 25% is often necessary to catch up.
Employer match is the percentage of your salary your employer contributes to your retirement plan, usually contingent on your own contribution. A typical match is 50% on the first 6% you contribute, meaning if you contribute 6% of salary the employer adds another 3%. Always contribute at least enough to get the full match — anything less leaves free money on the table.
Expected annual return should reflect your asset allocation. A 100% stock portfolio has historically returned about 7% real (inflation-adjusted); a 60/40 stock/bond portfolio about 5% real. As you approach retirement, gradually shifting toward bonds reduces volatility but also reduces expected return.
Inflation rate erodes purchasing power. The long-term U.S. average is about 3%, though shorter periods have been dramatically higher or lower. Always work in real (inflation-adjusted) terms when planning decades out.
Years in retirement defines your distribution horizon. Plan for 30 years even if your life expectancy projection is shorter — the cost of running out of money is far worse than the cost of leaving some behind. Couples should plan to the longer of the two life expectancies, not the average.
Expected Social Security is the monthly benefit you'll receive in retirement. The Social Security Administration provides personalized estimates at ssa.gov; pull your statement and use that number. For workers under 50, many planners suggest discounting the projected benefit by 20% to 25% to account for potential future benefit reductions.
The 4% Rule and Safe Withdrawal Rates
The most widely cited retirement spending rule is the 4% rule, derived from research by William Bengen and refined by the Trinity Study. It states that a retiree withdrawing 4% of their portfolio in year one and adjusting that dollar amount upward by inflation each subsequent year has historically had a very high probability of not running out of money over a 30-year retirement, even through periods like the 1970s stagflation or the 2000-2002 dot-com crash.
The math is simple: a $1 million portfolio supports $40,000 of inflation-adjusted spending per year. To replace $80,000 of annual income, you need $2 million. To replace $120,000, you need $3 million. This linearity is what makes the rule so useful for goal-setting.
Important caveats: 4% is appropriate for a 30-year retirement starting in your mid-60s. For early retirement (starting in your 40s or 50s), use 3% to 3.5%. For shorter retirement horizons, you can safely withdraw more. And the rule assumes a balanced portfolio of roughly 50/50 to 75/25 stock/bond split — both very aggressive and very conservative allocations underperform the rule's assumptions.
Catch-Up Contributions and Account Limits
The IRS sets annual contribution limits for retirement accounts. For 2025, those limits include 401(k) contributions of $23,500, IRA contributions of $7,000, and an additional $7,500 catch-up contribution available to those 50 and older. A 55-year-old maxing both a 401(k) and an IRA can save $39,000 per year in tax-advantaged accounts before counting the employer match. These limits typically increase modestly each year for inflation.
How to Use This Calculator Strategically
Run multiple scenarios. Test what happens if you retire at 62, 65, 67, and 70. The differences are usually large, both because of additional savings years and because Social Security benefits grow approximately 8% per year for each year you delay claiming past full retirement age.
Test sensitivity to returns. Run the calculator at 5% real and 7% real returns. If your plan only works at 7%, it's not robust. Conservative planning means the plan also works at 5%.
Model the impact of one more year of work. Working one extra year typically has three compounding effects: another year of savings, another year of growth on existing savings, one fewer year of withdrawals. The cumulative impact is usually equivalent to having saved 3% to 5% more for the entire career.
Use the calculator to set your savings rate target. Solve backwards: enter your retirement goal (the nest egg you'll need based on the 4% rule) and adjust your monthly contribution until the projected balance matches the goal. That number is your true required savings rate.
Retirement Calculator FAQ
How much should I have saved by each age?
A widely cited benchmark from Fidelity recommends having 1× your salary saved by 30, 3× by 40, 6× by 50, 8× by 60, and 10× by 67. These are rough guides; your actual target depends on expected retirement spending, retirement age, and pension or Social Security expectations.
Should I include Social Security in my plans?
Yes, but with some humility. Social Security currently provides 30% to 50% of pre-retirement income for typical workers, depending on earnings. Workers under age 50 should plan on receiving 75% to 80% of currently projected benefits to account for potential future trust fund shortfalls. Workers over 60 can largely plan on full projected benefits.
What's a safe withdrawal rate?
4% is the long-standing benchmark for a 30-year retirement starting in your 60s. Use 3.5% if you retire in your early 50s, 3% if you retire in your 40s, and you can safely use 4.5% to 5% for retirements expected to last 20 years or less.
Roth or traditional retirement accounts?
The general rule: Roth accounts are better when you expect higher tax rates in retirement than today; traditional accounts are better when you expect lower tax rates in retirement. Most workers in their 20s and 30s benefit from Roth contributions. Most workers in their peak earning years benefit from traditional contributions to lower current tax bills. Many planners recommend tax diversification — having both types of accounts so you have flexibility in retirement.
What about healthcare costs in retirement?
Healthcare is the single largest variable in retirement planning. Medicare begins at 65 but doesn't cover everything. Fidelity estimates a 65-year-old couple retiring today will spend roughly $315,000 on healthcare during retirement. If you retire before 65, you'll need a plan to bridge to Medicare — typically through ACA marketplace plans, COBRA continuation, or a working spouse's coverage.
This guide is for educational purposes only and is not financial, tax, or legal advice. Retirement planning involves significant uncertainty; consult a fee-only fiduciary financial advisor for guidance specific to your situation.