Retirement Calculator (compound projection + inflation-adjusted)
Enter your current age, target retirement age, current savings, monthly contribution, expected annual return, and inflation rate. The calculator projects compounded growth and applies the 4% rule for sustainable withdrawal.
- Projected balance (35 yrs)
- 1,015,589
- In today's dollars
- 532,705
- Total contributed
- 220,000
- Investment growth
- 795,589
- Monthly income (4% rule)
- 1,776
How it works
How the projection works
We compound your starting balance plus each monthly contribution at the annual return rate. The math is recursive: balance(month+1) = balance(month) × (1 + monthly_rate) + monthly_contribution. Over decades, even modest monthly amounts grow significantly because of compounding — the returns on prior returns compound on themselves.
We also project a 'today's dollar' value by deflating the nominal balance using your inflation rate. A million dollars in 30 years isn't worth a million today — at 2.5% inflation, $1M in 30 years has the purchasing power of about $475,000 today. The today-dollar figure is what you should compare to current cost of living.
What rate to assume
S&P 500 historical average is about 10% nominal / 7% real (after inflation) over very long periods. For retirement projections starting from 25 years out, 6-8% nominal is reasonable. Going below 5% is overly conservative for long horizons; going above 9% is optimistic given current valuations.
The closer to retirement, the more conservative your portfolio typically becomes (more bonds, less equity). For a 5-10 year window before retirement, expected return drops to 4-6% as bond allocation rises. This calculator uses a single rate for the entire horizon — for more nuanced projections, run scenarios with different rates.
The 4% rule
The 4% rule (Trinity Study, 1998) says you can safely withdraw 4% of your retirement savings in year 1, then adjust upward for inflation each year, with very high probability of not running out over 30 years. So $1M retirement savings supports $40,000/year (or about $3,333/month) of inflation-adjusted spending.
The rule has limitations — it's based on historical US stock/bond performance and may be optimistic for some future scenarios. Some experts now recommend 3-3.5% for safety. For early retirement (FIRE) with 50+ year horizons, 3% is more conservative. Use the 4% number as a rough sanity check, not a guarantee.
Frequently asked questions
›What return rate should I use?
For 25+ year horizons in a diversified stock-heavy portfolio: 6-7%. For shorter horizons or more conservative mix: 4-5%. Stock-only assumption: 7-8%. Use historical real returns (after inflation) — that's about 5-7% for stocks long-term.
›Why does today's dollars matter?
$2M in 35 years sounds amazing but at 3% inflation it's worth about $700K today. The today-dollar figure tells you what your retirement savings will buy in current terms — useful for planning current vs future expenses.
›Should I use pre-tax or after-tax contributions?
Depends on account type. 401(k) and traditional IRA are pre-tax (you'll pay tax on withdrawals). Roth IRA and Roth 401(k) are after-tax (tax-free withdrawals). For traditional accounts, your retirement balance is gross — you'll lose 15-30% to taxes during retirement.
›What if I get raises and increase contributions?
Run the calculator multiple times for each phase, or use a constant contribution that approximates your average. Real-world contributions often grow with salary; the calculator uses a flat number.
›Does this account for Social Security?
No. Social Security is a separate income stream. Project retirement savings here, then layer Social Security estimates on top for total retirement income planning.
›What's the 'safe withdrawal rate'?
Traditionally 4% (Trinity Study). For long retirements (FIRE, 40+ years), 3-3.5% is safer. The calculator shows 4% by default; adjust your monthly target if you want a different rate.
›How much do I need to retire?
Rule of thumb: 25× your annual spending needs (the inverse of the 4% rule). Spending $50K/year in today's dollars? Need $1.25M in today's dollars (or more nominal accounting for inflation by retirement).
›Does the data leave my browser?
No. All projection math runs locally; nothing is sent to any server.
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