403(b) vs 401(k): How to Calculate the Real Difference in Your Retirement

The Plans Share a Contribution Limit. That Is Where the Similarity Ends.

Both 403(b) and 401(k) plans carry the same IRS elective deferral limit: $23,500 in 2025 for participants under age 50, and $31,000 for those 50 and older with the standard $7,500 catch-up provision.

That shared ceiling creates a false sense of equivalence. The rules governing employer contributions, investment menu construction, fee disclosure requirements, and special catch-up provisions differ in ways that produce materially different outcomes at retirement.

Understanding those differences requires actual math, not broad comparisons.

Who Qualifies for Each Plan

The 401(k) is available to employees of for-profit companies. The 403(b) is restricted to employees of public schools, universities, hospitals, and 501(c)(3) nonprofit organizations.

If your employer offers a 403(b), you cannot simply opt into a 401(k) instead. Your plan type is determined by your employer's tax status. What you can control is how you allocate within your plan and whether you supplement it with an IRA.

The 15-Year Rule: A $15,000 Advantage Most 403(b) Participants Miss

Section 402(g)(7) of the Internal Revenue Code allows certain 403(b) participants to contribute up to $3,000 more per year beyond the standard IRS limit. The conditions are specific.

You must have worked for the same qualifying organization (educational institution, hospital, home health agency, or church) for at least 15 years. Your lifetime catch-up contributions under this provision cannot exceed $15,000 total. The IRS calculates an individual-specific limit based on your total prior contributions and years of service.

This provision does not exist in the 401(k) system. A teacher or hospital administrator who qualifies and contributes an additional $3,000 per year for five years, invested at a 7% annualized return, accumulates approximately $17,300 in additional retirement assets from that provision alone.

Most 403(b) participants never claim it. They either don't know it exists or assume their plan administrator will flag it automatically. Plan administrators are not required to proactively notify you.

Employer Matching: The Structure Matters More Than the Percentage

Both plan types allow employer matching. The comparison stops there.

How 401(k) Matching Typically Works

Most 401(k) plans follow a formula such as 100% match on the first 3% of compensation, or 50% match on the first 6%. Vesting schedules vary, but the match mechanics are straightforward and disclosed in the summary plan description.

How 403(b) Matching Often Differs

Many 403(b) plans, particularly in public K-12 education systems, offer no employer match at all. The plan functions as a supplemental savings vehicle layered on top of a defined-benefit pension. The pension is the primary retirement vehicle. The 403(b) is optional and unmatched.

Hospital and university 403(b) plans more commonly include matching contributions, often structured similarly to 401(k) formulas.

The practical implication: A teacher contributing 6% of a $72,000 salary to an unmatched 403(b) invests $4,320 per year of their own money. A private-sector employee at the same salary contributing 6% to a 401(k) with a 50% match on the first 6% invests $4,320 and receives an additional $2,160 from their employer. Over 25 years at 7% annualized return, that $2,160 annual employer contribution compounds to approximately $135,400. The teacher's plan left that money on the table by design, not by mistake.

The Fee Problem in 403(b) Plans

This is where the largest quantifiable gap lives.

Why 403(b) Fees Run Higher

Historically, 403(b) plans were sold through insurance companies as tax-sheltered annuity products. Many still are. Annuity wrappers add a layer of insurance charges, mortality and expense risk fees, and administrative fees that mutual fund-only plans do not carry.

A typical group variable annuity inside a 403(b) might carry total annual costs of 1.4% to 2.1%. A passively managed 401(k) invested in index funds might carry total costs of 0.05% to 0.30%.

A Worked Dollar Example

Assume two employees, both age 35, both contributing $15,000 per year for 30 years, both earning a 7% gross annualized return before fees.

Employee A (401(k), 0.10% total fee): Net annual return: 6.90% Balance at age 65: approximately $1,412,000

Employee B (403(b), 1.60% total fee): Net annual return: 5.40% Balance at age 65: approximately $1,094,000

The fee differential costs Employee B approximately $318,000 over 30 years. Same contribution rate. Same gross market return. Different plan cost structure.

This is not a theoretical scenario. It reflects the actual fee range documented in 403(b) plan audits conducted by university researchers and reported to the SEC.

When the 403(b) Wins

The 403(b) is not categorically inferior. Three scenarios favor it.

First, if your employer's 403(b) offers a quality low-cost investment menu, typically through providers such as Fidelity, Vanguard, or TIAA's traditional account options, the fee gap shrinks to negligible levels.

Second, if you qualify for the 15-year catch-up provision and have not maxed it out, the 403(b) offers a contribution capacity that no 401(k) can match.

Third, TIAA's Traditional Annuity account within a 403(b) provides contractually guaranteed minimum interest rates, currently ranging from 1% to 3% depending on contribution period, with historical crediting rates significantly above that floor. For conservative allocations near retirement, this guarantee has real value.

A Second Worked Example: The Catch-Up Comparison at Age 52

Consider a hospital nurse, age 52, with 17 years of service at the same nonprofit hospital. She earns $89,000 per year.

Her 403(b) contribution capacity in 2025:

• Standard limit: $23,500
• Age 50+ catch-up: $7,500
• 15-year service catch-up: $3,000 (subject to her specific calculation)
• Total potential deferral: $34,000

A 401(k) participant at age 52 with no qualifying service provision:

• Standard limit: $23,500
• Age 50+ catch-up: $7,500
• Total potential deferral: $31,000

The nurse can shelter $3,000 more per year. At a 6% annualized return over 13 years to age 65, that $3,000 annual premium compounds to approximately $55,700 in additional tax-deferred assets.

She should verify her specific catch-up limit with her plan administrator, since the calculation requires her total prior-year contributions and years of service to be factored in.

How to Audit Your Own Plan in Four Steps

Step 1: Identify Your Investment Menu's True Cost

Log into your plan portal. Find the fund fact sheets. Look for the "total annual operating expense" or "net expense ratio." Add any plan-level administrative fees disclosed in your annual fee disclosure notice (the 404a-5 notice your employer is legally required to provide).

Step 2: Compare Against a Benchmark

Vanguard's Target Retirement funds carry expense ratios of 0.08% to 0.15%. If your plan's blended cost exceeds 0.50%, you are paying excess fees that compound against you over time.

Step 3: Check Your Employer Match Formula and Vesting Schedule

An unvested employer match is not your money. If you are two years from full vesting, that timeline factors into any job-change calculation.

Step 4: Determine Whether You Qualify for Any Special Provisions

If you participate in a 403(b) and have 15 or more years with your current employer, request a written confirmation from your plan administrator on your 15-year catch-up availability. Do not assume they will raise it with you.

Run Your Own Numbers

The worked examples in this post use clean assumptions. Your actual outcome depends on your specific contribution rate, your plan's exact fee structure, your employer's match formula, your salary trajectory, and your asset allocation.

Those variables interact in ways that change the projected balance by tens of thousands of dollars. A 0.50% difference in annual fees on a $250,000 balance compounds to roughly $34,000 over 20 years at 7% growth. A missed catch-up provision costs you the full compounded value of those contributions.

The CalcMoney Retirement Calculator lets you input your actual plan parameters, not generic assumptions. Enter your current balance, contribution rate, employer match details, and estimated fee load. The calculator projects your balance at your target retirement age under your actual conditions.

That projection is the number worth knowing. Use it to decide whether your current allocation serves you, whether a plan change makes financial sense, and whether you qualify for contribution provisions you have not yet claimed.

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Run your 403(b) or 401(k) projection now with the CalcMoney Retirement Calculator →