A defined-benefit (DB) pension — the traditional "final salary" or "career average" plan — promises you a fixed monthly payment for life once you retire, based on a simple three-part formula rather than on how your investments perform. This pension calculator estimates exactly what that promised income looks like: your annual pension, your monthly check, the share of your working salary it replaces, and the total value of benefits you can expect to collect.
Unlike a 401(k) or IRA, where the outcome depends on markets and your own contributions, a DB plan puts the risk on the employer. The trade-off is that the benefit is formula-driven, so understanding the math is the single most useful thing you can do to plan around it.
How to Use
- Enter your Final Average Salary. This is usually your highest or average pensionable pay over your last three to five years of service, not your very last paycheck. Use the figure your plan's benefit statement references.
- Set your Years of Service — the total years (and part years, as decimals) you were an active member of the plan. Twenty years and six months counts as 20.5.
- Choose your Accrual Rate. Most public-sector and legacy corporate plans earn 1%–2% of salary per year of service. Check your Summary Plan Description; a common value is 1.5%.
- Optionally, set Years in Retirement — how long you expect to collect. This drives the lifetime benefit estimate and is not part of the core annual formula.
- Read the result card: Annual Pension, Monthly Pension (the highlighted headline number), your Income Replacement Rate, and the Estimated Lifetime Benefit.
Slide the inputs and watch every figure update instantly. Raise the accrual rate or years of service to see how much a single extra year of service is worth, or lower the final salary to stress-test what happens if you are laid off a few years early.
The Defined-Benefit Pension Formula
The annual pension is the product of three numbers, and nothing else:
Annual Pension = Final Salary × Years of Service × Accrual Rate
Where:
- Final Salary is your pensionable pay used in the plan formula (often a 3- to 5-year average).
- Years of Service is your credited service time, including purchased or bought-back years.
- Accrual Rate is the percentage of salary earned each year — for example 1.5%.
Your Monthly Pension is simply the annual figure divided by 12. Your Income Replacement Rate is the annual pension divided by your final salary, which equals your years of service times your accrual rate.
Worked example on an $85,000 final salary with 25 years of service at a 1.5% accrual rate:
Annual Pension = $85,000 × 25 × 0.015 = $31,875 per year, or $2,656.25 per month.
The replacement rate is 25 × 1.5% = 37.5% of final salary. If you expect to collect for 20 years, the estimated lifetime benefit is $31,875 × 20 = $637,500.
Notice how linear the formula is: every extra year of service adds 1.5% of final salary to your annual pension, and every $10,000 of final salary adds 25 × 1.5% = $3,750 per year. That predictability is what makes DB pensions prized — and why the "last few years" before retirement are so valuable.
Replacement Rate: What Is a Good Target?
Financial planners often advise that retirement income should replace roughly 70%–80% of your pre-retirement salary to maintain your standard of living. A single-career DB pension at 30 years and 2% accrual reaches 60% replacement on its own — before Social Security, personal savings, or a 401(k). That is why long-tenured public employees often retire feeling financially secure.
Conversely, 25 years at 1.5% replaces only 37.5%. If your final salary is $85,000, that is about $31,875 a year — a meaningful gap you would need to fill with personal savings, Social Security, or part-time work. Use the replacement rate on the result card as your quick gap indicator.
Final Average vs Career Average
Some newer (career-average) plans do not use your highest salary. Instead, each year of contributions earns a small slice based on that year's own pay. The math still multiplies service years by an accrual rate, but applied to your average — not peak — salary. A final-salary plan generally pays more, especially for fast risers; a career-average plan is cheaper for employers and tends to pay a smoother, more modest benefit. This calculator uses the classic final-salary formula; if your plan is career-average, enter your career-average salary in place of the final salary.
Examples
Example 1 — The 30-year public employee. A teacher retires at a $90,000 final average salary after 30 years in a 2% plan. Annual pension = $90,000 × 30 × 0.02 = $54,000 per year, about $4,500 per month, a 60% replacement rate. Over a 20-year retirement that is roughly $1,080,000 in lifetime benefits.
Example 2 — The mid-career changer. Someone leaves after 18 years at a 1.5% plan with a $70,000 final salary. Annual pension = $70,000 × 18 × 0.015 = $18,900 per year, or $1,575 per month — about a 27% replacement rate. The calculator makes the gap obvious, which is why many mid-career leavers must lean harder on a 401(k).
Example 3 — The high-earner extreme. An executive with a $1,200,000 final salary and 30 years at 2% accrual earns $1,200,000 × 30 × 0.02 = $720,000 per year, or $60,000 per month, a 60% replacement rate. In practice, IRS Section 415 and plan benefit limits cap such six-figure accruals, so the real payable amount is usually lower — a reminder to confirm your plan's maximum.
FAQ
How is a defined-benefit pension calculated?
It uses a fixed formula: Annual Pension = Final Salary × Years of Service × Accrual Rate. The result is then divided by 12 for a monthly payment. This is the same formula used by most public-sector and traditional corporate pension plans, and it does not depend on investment returns.
What is a good accrual rate for a pension?
Common accrual rates are between 1% and 2% of salary per year of service. A 1.5% rate is typical for many legacy plans; 2% is generous and common in public safety and teacher plans. Multiply the rate by your expected years of service to estimate your replacement rate — 30 years at 2% gives a 60% pension.
What does "final average salary" mean?
It is usually your highest consecutive three- to five-year average of pensionable earnings, not necessarily your last paycheck. Overtime, bonuses, and side income are often excluded. Check your plan's Summary Plan Description for the exact definition, because it is the single biggest lever on your benefit.
How much will my pension replace of my salary?
Your replacement rate equals your years of service multiplied by your accrual rate. For example, 25 years at 1.5% replaces 37.5% of final salary, while 30 years at 2% replaces 60%. Add Social Security and personal savings to reach the 70%–80% retirement-income target most planners recommend.
Can I take my pension as a lump sum?
Some plans offer a lump-sum option instead of a lifetime annuity. The choice is major: a monthly check guarantees income for life regardless of how long you live, while a lump sum gives flexibility but exposes you to investment and longevity risk. Compare the lump-sum offer against the monthly annuity value, and consult a fiduciary adviser before deciding.
Does buying extra years of service pay off?
Often yes. Because each added year raises the pension by a fixed percentage of your final salary, bought-back service can be cheap relative to the lifetime benefit it secures. Divide the purchase cost by the extra annual pension to estimate your payback period — a payback under your life expectancy is usually attractive.
Disclaimer
This pension calculator is provided for informational purposes only and does not constitute financial, tax, or legal advice. Estimates are based on the standard defined-benefit formula and the exact inputs you enter; your actual benefit depends on your specific plan's rules, final-average salary definition, cost-of-living adjustments, early-retirement reductions, survivor options, and legal benefit limits. Always verify your projected pension directly with your plan administrator or a licensed retirement professional before making retirement decisions.