401(k) 提撥計算機

What Is a 401(k)?

A 401(k) is a tax-advantaged retirement savings plan sponsored by your employer. You contribute pre-tax dollars (traditional) or after-tax dollars (Roth), and the money grows tax-deferred until withdrawal.

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2026 Contribution Limits

| Type | Limit | |------|-------| | Employee (under 50) | $23,500 | | Employee (age 50+, catch-up) | $31,000 | | Combined (employee + employer) | $70,000 |

The $70,000 combined limit matters if your employer offers a mega backdoor Roth strategy — after-tax voluntary contributions above the standard employee limit (up to the $70,000 total cap) can be converted to Roth, generating tax-free growth.

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The Power of Employer Match

Employer matching is the single best return available in personal finance — it is an immediate 50–100% return on every matched dollar. Always contribute at least enough to capture the full employer match before investing anywhere else.

Example: $80,000 salary, 50% match up to 6%

• Your contribution: $4,800/year (6% of salary)
• Employer match: $2,400/year (50% of $4,800)
• Total invested annually: $7,200 — for a $4,800 out-of-pocket cost

Not capturing the full match is equivalent to leaving part of your salary on the table.

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Tax Savings: Traditional vs Roth 401(k)

| | Traditional 401(k) | Roth 401(k) | |-|--------------------|-------------| | Contribution | Pre-tax (reduces W-2 income) | After-tax (no current deduction) | | Growth | Tax-deferred | Tax-free | | Withdrawal in retirement | Taxed as ordinary income | 100% tax-free | | RMDs required? | Yes (starting at age 73 or 75) | No (from 2024 onwards) | | Best when | You expect lower taxes in retirement | You expect higher taxes in retirement |

Traditional contributions reduce your W-2 income dollar-for-dollar. At a 22% marginal rate, a $10,000 contribution saves $2,200 in federal income tax this year. In high-tax states like California (13.3%) the combined tax savings can reach $3,530.

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Compounding Over Time

Time is your most powerful variable. A 30-year-old contributing $10,000/year with 50% employer match ($15,000 total) at 7% annual return accumulates:

| Age | Balance | |-----|---------| | 40 | ~$207,000 | | 50 | ~$612,000 | | 60 | ~$1,510,000 | | 65 | ~$2,140,000 |

Starting 10 years later (at age 40 instead of 30) with the same contributions cuts the age-65 balance by more than half — roughly $920,000 vs $2,140,000.

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Vesting: When Employer Contributions Are Truly Yours

Your own contributions are always 100% vested immediately. Employer contributions vest on a schedule set by your plan:

• Immediate vesting: You own employer contributions right away
• Cliff vesting: 0% until a threshold date (e.g., 3 years), then 100%
• Graded vesting: Partial ownership building over several years (common: 20% per year from year 2–6)

Before leaving a job, check the vesting schedule — departing before full vesting forfeits unvested employer contributions.