How to Plan Your Retirement Savings
This calculator projects your retirement savings forward using compound growth, then applies the "4% rule" to estimate sustainable monthly income — a widely cited (though debated) guideline suggesting you can withdraw 4% of your portfolio annually with a low risk of running out of money over a 30-year retirement.
The earlier you start, the less you need to contribute monthly to reach the same goal, since compound growth has more time to work. Someone starting at 25 needs roughly half the monthly contribution of someone starting at 35 to reach the same retirement balance by 65.
The 4% Rule Formula
Sustainable Annual Withdrawal = Portfolio Balance × 4%
Sustainable Monthly Income = (Portfolio Balance × 4%) ÷ 12
This rule originated from the "Trinity Study" and is a guideline, not a guarantee — actual safe withdrawal rates depend on market conditions, your specific retirement length, and portfolio composition.
Worked Example
Example
A 30-year-old with $20,000 saved, contributing $500/month at a 7% average annual return, would have approximately $1,020,000 by age 65. Applying the 4% rule, that supports about $3,400/month in sustainable retirement income — without ever touching the principal balance.
Tips to Improve Your Retirement Outlook
- Capture any employer 401k match first — it's an immediate, guaranteed return that this calculator doesn't separately account for.
- Increase contributions with raises — even a 1% annual increase in your savings rate compounds significantly over a career.
- Don't panic-sell during downturns — market volatility is normal; the 7% average return already factors in both up and down years historically.
- Revisit your plan every few years — life changes (income, expenses, retirement age goals) should update your monthly contribution target.
Frequently Asked Questions
Is the 4% rule still considered safe? ▼
The 4% rule remains a widely used starting point, though some financial planners now suggest 3-3.5% for extra safety margin given longer life expectancies and uncertain future market returns. It's best used as a rough guideline rather than a precise guarantee.
What if I'm starting retirement savings late? ▼
Starting later means you'll need to contribute significantly more per month to reach the same goal, since there's less time for compounding. Catch-up contributions (available after age 50 for 401k/IRA accounts in the US) can help, as can adjusting your target retirement age or planned monthly spending.
Should I include Social Security in this calculation? ▼
This calculator focuses purely on personal savings growth and doesn't include Social Security, pensions, or other income sources. For a complete retirement picture, add your expected Social Security benefit (available via ssa.gov) on top of the sustainable monthly income shown here.
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