How the Four Tools Work
Retirement planning isn't one calculation — it's several related questions people ask at different points in life. This page bundles four of them into one place. How Much to Retire projects your balance forward from today given your current savings and contribution rate, then checks it against what you'll likely need. How to Save works backward from a target number to tell you the monthly contribution required to hit it. Withdrawal Amount estimates a sustainable monthly income once you've actually reached retirement. How Long It Lasts answers the question people ask when they already have a lump sum and a spending rate in mind: will it outlive me, or will I outlive it?
A Worked Example
Take a 30-year-old earning $80,000, saving 10% of income annually, with $20,000 already saved, expecting 3% raises and a 6% average investment return. Run those numbers through the "How Much to Retire" tab and the projected balance at 65 lands around $1.45 million — of which roughly $1.1 million came from contributions and the rest from investment growth compounding over 35 years. That's the core lesson of retirement math: the earlier money goes in, the more of the final balance comes from growth rather than your own contributions.
How Much Should You Save? Three Rules of Thumb
The 10% Rule
Save 10–15% of pre-tax income throughout your working years. Starting at age 25, consistently saving 10% can realistically build toward a seven-figure balance by traditional retirement age, purely through the combination of contributions and compounding.
The 80% Rule
Plan for retirement income equal to roughly 70–80% of your pre-retirement income. Many expenses (commuting, retirement account contributions themselves, payroll taxes) disappear or shrink in retirement, which is why most people need somewhat less than their working income to maintain a similar lifestyle — though this varies a lot based on individual plans.
The 4% Rule
Divide your desired annual retirement income by 4% to estimate the nest egg required to sustain it — for example, needing $80,000/year implies a target of roughly $2 million. This widely-cited guideline comes from historical research on how large a withdrawal rate a diversified portfolio can typically sustain over a multi-decade retirement without running out, though it's a planning heuristic, not a guarantee.
Common Sources of Retirement Income
- Social Security — designed to replace roughly 40% of a typical worker's income, not the whole thing. Benefits scale with lifetime earnings but not proportionally — lower earners get a bigger percentage replacement than higher earners.
- Employer plans (401(k), 403(b)) — pre-tax contributions that grow tax-deferred, often with an employer match that amounts to free money on top of your own savings.
- IRAs and Roth IRAs — individual accounts with their own tax treatment: traditional IRAs defer tax until withdrawal, Roth IRAs are taxed going in but withdrawals in retirement are generally tax-free.
- Pensions — less common than a generation ago outside the public sector, but still a meaningful income source for some retirees, typically paid as a fixed monthly amount for life.
- Personal investments and savings — brokerage accounts, real estate, and other assets that aren't tax-advantaged but have no contribution limits.
To turn any of those rules into an actual monthly figure, or to work backwards from a target you have already set, use our SIP calculator.
Why Inflation Matters More Than You'd Think
At just 3% annual inflation, prices roughly double every 24 years — meaning a retiree who plans a 30-year retirement needs their income to more than double in nominal terms just to maintain the same purchasing power by the end. This calculator's withdrawal-phase tools account for this by using a real (inflation-adjusted) return rather than the raw nominal return, so the sustainable income figure reflects actual buying power staying roughly level throughout retirement, not just a flat dollar amount that quietly loses value each year.
Common Retirement Planning Mistakes
- Underestimating life expectancy — running out of money at 82 because you planned to 80 is a real risk; padding your life-expectancy estimate by a few years is cheap insurance.
- Ignoring employer match — not contributing enough to capture a full 401(k) match is leaving guaranteed, immediate return on the table.
- Front-loading risk near retirement — a market downturn in the years right before or after retiring can do outsized damage to a portfolio, since there's less time to recover before withdrawals begin.
- Treating Social Security as a full replacement — at roughly 40% income replacement, Social Security alone is rarely enough for a comparable standard of living.
- Not adjusting the plan over time — a projection made at 30 should be revisited periodically as income, savings rate, and market returns actually unfold.
One more that is easy to miss: letting the mix drift. A portfolio built at 60% stocks can be sitting at 75% after a long bull run, which is a very different amount of risk to carry into the years just before you stop working. Our portfolio allocation calculator shows how far each holding has moved and what it would take to bring it back.
Education is often the other large goal running alongside retirement, and our college cost calculator projects tuition inflation against what you have saved so far.
Frequently Asked Questions
What return rate should I assume?
A commonly used long-run assumption for a diversified stock-heavy portfolio is in the 6–8% nominal range, though this varies with asset allocation, time horizon, and risk tolerance — more conservative portfolios (bonds, cash) should use a lower assumption, and returns closer to retirement are often assumed to be lower as portfolios shift toward safety.
Is the 4% rule still considered accurate?
It remains a widely referenced starting point, though it's been debated — some research suggests a somewhat lower rate is more conservative for very long retirements, while others argue a dynamic (variable) withdrawal strategy that adjusts with market performance can sustain a higher initial rate. Treat 4% as a reasonable planning anchor, not a fixed rule.
Should I include Social Security in my projection?
Yes — the "Other Monthly Income" field in the first tab is built for this. Leaving it out will overstate how much your personal savings alone need to cover, which can lead to either overly conservative spending in retirement or unnecessary anxiety about the numbers.
Why does my required monthly savings look so high?
Starting later or targeting a larger nest egg both increase the required contribution significantly, since there's less time for compounding to do the work — a target that's easy to hit starting at 25 can look daunting starting at 45 for the exact same eventual goal.
What if I'm already retired — is this calculator still useful?
Yes — the "Withdrawal Amount" and "How Long It Lasts" tabs are built specifically for people already at or near retirement, helping answer whether a current balance and spending rate are sustainable for the years ahead.
This calculator is provided for educational and estimation purposes only and does not constitute financial advice. Consult a licensed financial advisor for guidance specific to your retirement situation.