Retirement Planning: How Much Do You Really Need?

The most common retirement question is "how much money do I need?" The answer depends on when you want to retire, where you live, and what lifestyle you want. But we can get surprisingly precise with some simple math. This guide walks you through the formulas, the account types, the tax strategies, and the specific action steps for every decade of your working life.

The 4% Rule: Your Retirement Number

The most widely used retirement benchmark comes from the Trinity Study: you can safely withdraw 4% of your portfolio annually without running out of money over a 30-year retirement. This means your retirement number is your annual expenses multiplied by 25.

Retirement Accounts Explained

The U.S. tax code provides several retirement account types, each with different tax advantages. Understanding the differences can save you hundreds of thousands in taxes over your lifetime.

Traditional 401(k): Employer-sponsored. Contributions reduce your taxable income today (tax-deferred). You pay taxes when you withdraw in retirement. The 2026 contribution limit is $23,500 ($31,000 if age 50+). If your employer matches contributions, always contribute at least enough to get the full match — it's a guaranteed 50-100% return.

Roth 401(k): Same employer-sponsored plan, but contributions are made with after-tax dollars. Withdrawals in retirement are completely tax-free, including all growth. Choose Roth if you expect to be in a higher tax bracket in retirement than you are now, or if you want tax diversification.

Traditional IRA: Individual account. Contributions may be tax-deductible (depends on income and whether you have a workplace plan). Grows tax-deferred; taxed on withdrawal. 2026 contribution limit is $7,000 ($8,000 if age 50+).

Roth IRA: Contributions are after-tax, but all growth and withdrawals are tax-free forever. Income limits apply for direct contributions (approximately $161,000 for single filers, $240,000 for married filing jointly in 2026). If you exceed income limits, use the "backdoor Roth" strategy: contribute to a Traditional IRA, then convert to Roth. This is legal and widely used.

HSA (Health Savings Account): Often called the "stealth retirement account." Triple tax advantage — tax-deductible contributions, tax-free growth, and tax-free withdrawals for medical expenses. After age 65, you can withdraw for any purpose (taxed like a Traditional IRA but without penalty). 2026 family contribution limit is approximately $8,550.

The Power of Starting Early

Time is the most powerful variable in retirement planning. The difference between starting at 25 and starting at 35 is enormous, even with smaller contributions. Assuming a 10% average annual return in a diversified stock index fund:

Starting at 25 with $300/month produces nearly $1.9 million — on just $144,000 in total contributions. The other $1.75 million is compound growth. Starting at 35, you'd need to contribute $500/month to reach a similar outcome, and you'd still fall short. Every year you wait costs you exponentially.

Strategy by Decade

20s — Build the habit: Even $100-300/month matters enormously at this age because you have 35-45 years of compounding ahead. Max out employer 401(k) match first, then open a Roth IRA. Invest in a target-date fund or a total stock market index fund (like VTI or VTSAX). Don't try to pick individual stocks. Your job in your 20s is to build the savings habit and let time do the heavy lifting.

30s — Accelerate: Income typically rises significantly in this decade. Every raise should go partly toward increasing retirement contributions. Aim to save 15-20% of gross income for retirement. If you can max out your 401(k) ($23,500) plus a Roth IRA ($7,000), that's $30,500/year and you're on an excellent trajectory. Start an HSA if eligible.

40s — Optimize: This is the decade for tax optimization. Diversify between Traditional (pre-tax) and Roth (post-tax) accounts for tax flexibility in retirement. Catch-up contributions become available at 50. Begin thinking seriously about your target retirement date and whether your savings rate supports it. Use CashTwo's investment return calculator to run projections.

50s — Finalize: Take advantage of catch-up contributions ($31,000 to 401(k), $8,000 to IRA). Begin shifting asset allocation from aggressive growth toward a more balanced portfolio. Start projecting Social Security benefits and deciding when to claim (delaying until 70 increases your monthly benefit by approximately 8% per year after full retirement age). Create a detailed retirement budget.

60s — Transition: Develop a withdrawal strategy that minimizes taxes. Typically this means drawing from taxable accounts first, then Traditional retirement accounts, then Roth accounts last (since Roth has no required minimum distributions and grows tax-free). Consider delaying Social Security if you have enough savings to bridge the gap. Every year of delay adds significantly to your lifetime benefits.

Common Retirement Planning Mistakes

Cashing out when changing jobs: When you leave an employer, you can roll your 401(k) into an IRA or your new employer's plan tax-free. Cashing out triggers income taxes plus a 10% early withdrawal penalty if you're under 59.5. A $50,000 cash-out could cost you $15,000-20,000 in taxes and penalties, plus the lost decades of growth on that money.

Being too conservative too early: In your 20s-40s, being 100% in stocks is historically optimal for long-term retirement accounts. The market will drop — sometimes 30-40% — but you have decades to recover. A 30-year-old with 60% bonds is leaving significant growth on the table. Bond allocation should increase as you approach retirement, not before.

Underestimating healthcare costs: The average retired couple spends approximately $315,000 on healthcare throughout retirement (not including long-term care). Medicare doesn't cover everything, and premiums, deductibles, and out-of-pocket costs add up. Factor healthcare into your retirement budget explicitly.

Ignoring inflation: $60,000/year in today's dollars will feel like $36,000 in 25 years at 2% inflation. Your retirement portfolio must grow faster than inflation, which is why holding growth investments (stocks) even into early retirement is important. The 4% rule already accounts for inflation adjustments.

The FIRE Movement: Retiring Early

Financial Independence, Retire Early (FIRE) applies the same math but with higher savings rates. Instead of saving 15-20% of income, FIRE practitioners save 40-70%. The result is reaching financial independence in 10-15 years instead of 35-40 years.

Lean FIRE targets $25,000-40,000/year in expenses ($625K-$1M portfolio). Fat FIRE targets $80,000-120,000/year ($2M-$3M portfolio). Coast FIRE means saving enough early that compound growth alone will fund traditional retirement at 65, then working only enough to cover current expenses.

FIRE isn't for everyone, but the underlying principles — spend less than you earn, invest the difference in low-cost index funds, and let compound growth work — apply universally.