How the 403(b) Calculator Works
What each field means, how the math works, and what the results actually tell you.
The inputs
Current 403(b) balance
Your account balance today, before this year's contributions. You can find this on your most recent account statement or by logging into your plan provider's website. If you have multiple 403(b) accounts from different employers, you can add them together or run separate calculations.
This number compounds from day one. A $45,000 balance growing at 6% for 25 years becomes roughly $193,000 without adding a single dollar. That's the power of money you've already saved.
Your annual contribution
The total dollar amount you put in per year, not the percentage. If you contribute 5% of a $60,000 salary, enter $3,000. The 2026 IRS limit for employee elective deferrals is $23,500. If you're 50 or older, you can contribute up to $31,000 once you include the $7,500 catch-up.
The calculator flags contributions over $23,500 as an error to prevent projections based on an illegal contribution amount. If you're eligible for the age-50 catch-up, enter your full intended contribution up to $31,000 and use the 15-year rule toggle separately if it also applies.
Employer match (per year)
The flat dollar amount your employer contributes annually. Many nonprofit and school district plans offer a fixed match rather than a percentage match. Enter whatever your employer actually puts in, or leave it at $0 if your employer doesn't match.
This number has a disproportionate impact on your ending balance because employer dollars compound just like yours do. The calculator shows you the explicit dollar value of your match in the results, specifically the difference between your projected balance with the match versus without it.
Years until retirement
How many full years you plan to keep contributing before you stop working. The calculator applies your annual contributions for exactly this many years, then stops. It doesn't model partial years.
A rough rule: each additional year of contributions adds approximately one year's contribution plus the growth that money earns over the remaining time. At 6% and 20 years to go, each additional $10,000 you contribute today adds about $32,000 to your final balance.
Expected annual return
The assumed rate of return on your investments, expressed as a percentage. This is the biggest lever in any long-term projection and also the least certain.
Historical context: the S&P 500 has returned roughly 10% per year before inflation since 1926. Adjusted for inflation, closer to 7%. A diversified portfolio including bonds typically lands somewhere between 5% and 7% real. The default of 6% is a conservative middle estimate. Higher allocations to stocks can support a higher assumption; higher allocations to bonds or cash warrant a lower one.
Don't anchor too hard on any single number. The results panel shows you a single projection at the rate you choose. Real returns vary year to year, sometimes dramatically.
15-year rule catch-up
A toggle specific to 403(b) plans. If you've worked for the same qualifying employer (public school, 501(c)(3) nonprofit, hospital, or church) for at least 15 years, and your average annual contribution over that period has been below $5,000, you may contribute an additional $3,000 per year. The IRS caps the lifetime total of these extra contributions at $15,000.
Not every plan supports this feature even when the participant qualifies. Confirm with your HR department or plan administrator before assuming you can use it. When enabled, the calculator adds $3,000 to your annual contribution total for every year of the projection. It does not automatically cap at 5 years or $15,000 lifetime, since you may have already used some of this allowance. Adjust accordingly.
The outputs
Projected balance at retirement
The future value of your 403(b) after the number of years you specified, calculated using the standard compound growth formula:
Where PV is your current balance, r is the annual return rate, n is years until retirement, and PMT is your total annual contributions (your contribution plus employer match plus any 15-year rule amount). The formula assumes contributions are made once per year at the start of each period.
Monthly income (4% rule)
The projected balance multiplied by 4%, then divided by 12. The 4% rule comes from the Trinity Study, a 1998 analysis by three finance professors at Trinity University, which found that a retiree withdrawing 4% of their initial portfolio annually had a high probability of not running out of money over a 30-year retirement, even through historical market downturns including the Great Depression.
It's a starting point, not a guarantee. Actual sustainable withdrawal rates depend on your asset allocation, the sequence of returns you experience in early retirement, your other income sources, and how long you live. Some planners use 3.5% for longer retirements; others use 4.5% for shorter ones. The calculator uses 4% as a widely understood benchmark.
Total contributions vs. total growth
The stacked bar breaks your projected balance into two pieces: money you put in (contributions, including employer match and starting balance), and money the market added (growth). Over long time horizons, growth typically dominates. At 6% for 30 years, a dollar invested today becomes roughly $5.74, meaning growth accounts for about 83% of the ending value.
This ratio is why starting early matters more than saving more later. Ten years of compounding at the beginning is worth far more than ten years of compounding at the end.
Employer match value
The difference between your projected balance with the employer match and the projected balance without it. This is the compounded value of every dollar your employer contributed. If your employer puts in $2,000 per year for 25 years at 6%, the compounded value of that match alone is over $109,000. That's the number you'd be leaving behind by not capturing the match.
Frequently asked questions
Does this calculator account for inflation?
No. All figures are in nominal dollars, not inflation-adjusted. A projected balance of $800,000 in 25 years will have less purchasing power than $800,000 today. To get a rough inflation-adjusted estimate, use a lower return rate. If you expect 6% nominal returns and 2.5% inflation, entering 3.5% in the return field gives you a projection in today's dollars.
Does the calculator account for investment fees?
No. Expense ratios and administrative fees reduce your net return and aren't modeled here. A 403(b) plan with a 1% annual fee effectively cuts your return by 1 percentage point. If your plan's average expense ratio is 0.8%, subtract that from your expected return before entering it. Low-cost index funds in a 403(b) typically have expense ratios under 0.1%.
What if my contribution changes over time?
The calculator assumes you contribute the same amount every year for the full projection period. If you plan to increase contributions over time, one approach is to use your average expected annual contribution rather than your current one. If you're planning a specific ramp, running the calculation in two segments can give a more accurate result.
Why does the 15-year rule add $3,000/yr for the entire projection period?
The calculator doesn't know how many years of the 15-year rule you've already used, or whether you'll remain eligible for the full projection period. It adds $3,000 for every year you specify. If you've already used 3 years of the rule, you have at most 2 years left before hitting the $15,000 lifetime cap. Adjust your contribution input to reflect that.
Can I use this for a 403(b) Roth account?
The projection math is the same whether your contributions go into a traditional pre-tax 403(b) or a Roth 403(b). The difference is when you pay taxes: pre-tax now and taxable on withdrawal, or post-tax now and tax-free on withdrawal. This calculator doesn't model tax impact. For Roth comparisons, a tax advisor can run the after-tax numbers for both options based on your current and expected future tax rates.