Updated October 30, 2026. Quick answer: The Teachers’ Retirement System of Illinois pays 2.2% of your final average salary for each year of service, up to a 75% maximum. Tier I members (members before 2011) average their highest 4 years and can retire at 62 with 5 years, 60 with 10 or 55 with 35; Tier II members average their highest 8 years and need age 67 with 10 years for an unreduced annuity. Computed for a Tier I member with 30 years and a $80,000 final average salary retiring at 60, that is $52,800 a year (computed), or $4,400 a month (computed). Enter your own numbers below; the figure is the standard annuity, before a reversionary annuity or any other election.
Calculate your TRS Illinois annuity
This page applies the average salary and service credit formula in the TRS member guides to your tier, service, age and final average salary. It runs on this page and sends nothing anywhere. Your tier is the one TRS shows on your account; Tier I and Tier II are separate guides on the TRS site. Enter your service credit as shown on your statement, whole years and months.
For a decision, use TRS’s own tools and staff at trsil.org. This page is the published formula, shown so you can see the arithmetic.
The formula, as TRS prints it
For service after June 1998 the Tier I guide says “For post-June 1998 service, you receive 2.2 percent for each year of service.” The Tier II guide says “Benefits will still be determined by the formula of 2.2 percent multiplied by final average salary multiplied by years of creditable service.” Both guides cap the annuity: Tier II says “The maximum benefit a member can receive is 75 percent of his or her final average salary.” and Tier I adds “If you are qualified to receive a benefit of at least 74.6 percent of final average salary, we will round this percentage up to the 75 percent maximum retirement benefit.” The Tier I guide gives the effect: “you will receive the maximum benefit with 34 years of service credit if you are eligible for an unreduced annuity”.
The salary average differs by tier. Tier I: “The final average salary will be based on the four highest years within the last 10 years of creditable service.” Tier II: “The final average salary will be based on the eight highest years within the last 10 years of creditable service.” Tier II also limits the salary itself: “In determining a final average salary, no member’s salary will exceed a limit that is tied to the Consumer Price Index.” The guide does not print the limit, so enter your final average salary after that limit if it applies to you.
Worked example, calculated for Tier I: 30 years at 2.2% is 66% of a $80,000 final average salary = $52,800 a year (computed), $4,400 a month (computed), with no reduction because the member is 60 with at least 10 years. With 35 years the formula gives 77%, above the maximum, so the annuity is held at 75% of $80,000 = $60,000 a year (computed).
When the annuity is not reduced
In addition to ending covered service, a Tier I member must meet one of these age and service combinations, which the guide prints in a table: 5 years of service at age 62, 10 years at age 60, 20 years at age 55 (reduced annuity) or 35 years at age 55. The guide adds a footnote the calculator does not apply: “If you are eligible to receive a retirement annuity of at least 74.6 percent of the final average salary and will reach age 55 between July 1 and Dec. 31, we consider you to have attained age 55 on the preceding June 1.” A member within a few months of 55 should ask TRS. Tier II is stricter: “Tier 2 requires teachers and administrators to be 67 years old and have accumulated at least 10 years of service credit in order to qualify for nonreduced benefits that a member has earned.”
Retiring early: the reductions, computed
Tier I: “If you retire between the ages of 55 and 60 with at least 20 but fewer than 35 years of service, your retirement annuity is reduced by 6 percent for each year (half percent per month) that you are under age 60.” Tier II: “Tier 2 members may retire at age 62 with at least 10 years of service but will receive retirement benefits reduced 6 percent for every year the member is under age 67.” Tier I states the monthly rate; the Tier II guide states only the yearly rate and no part-year rule, so this calculator prints a Tier II reduced figure only when you enter your age in whole years.
Worked example, calculated for Tier I: 22 years at 2.2% is 48.4% of $80,000 = $38,720 a year (computed) before the reduction. At 57 the member is 36 months under 60, so the reduction is 36 x 0.5% = 18% and the annuity is $31,750.40 a year (computed), $2,645.87 a month (computed). Calculated for Tier II: 25 years at 2.2% is 55% of $70,000 = $38,500 a year (computed) before the reduction. At 62 the member is 5 years under 67, so the reduction is 5 x 6% = 30% and the annuity is $26,950 a year (computed), $2,245.83 a month (computed).
| Tier I age at retirement | Reduction | Annual annuity | Monthly annuity |
|---|---|---|---|
| 55 | 30.0% | $30,800 (computed) | $2,566.67 (computed) |
| 56 | 24.0% | $33,440 (computed) | $2,786.67 (computed) |
| 57 | 18.0% | $36,080 (computed) | $3,006.67 (computed) |
| 58 | 12.0% | $38,720 (computed) | $3,226.67 (computed) |
| 59 | 6.0% | $41,360 (computed) | $3,446.67 (computed) |
The Tier I table holds 25 years and a $80,000 final average salary fixed and moves only the age; every row meets the 20-year condition.
| Tier II age at retirement | Reduction | Annual annuity | Monthly annuity |
|---|---|---|---|
| 62 | 30.0% | $26,950 (computed) | $2,245.83 (computed) |
| 63 | 24.0% | $29,260 (computed) | $2,438.33 (computed) |
| 64 | 18.0% | $31,570 (computed) | $2,630.83 (computed) |
| 65 | 12.0% | $33,880 (computed) | $2,823.33 (computed) |
| 66 | 6.0% | $36,190 (computed) | $3,015.83 (computed) |
The Tier II table holds 25 years and a $70,000 final average salary fixed and moves only the age, in whole years.
What the annuity does not decide
1. The annuity option. TRS pays a standard annuity unless you elect a reversionary annuity, and the guide describes the standard annuity as the largest lifetime amount. A reversionary annuity trades some of that for a payment to a beneficiary; the wider single life versus survivor trade is on the single life versus joint and survivor page.
2. Which choices the tier leaves. The system-level decisions are on the TRS Illinois retirement decisions page, and the state tax treatment is on the Illinois pension tax page. Federal tax is separate: “The taxable part of your pension or annuity payments is generally subject to federal income tax withholding.” The withholding form is described on the IRS page for Form W-4P: “so your payer can withhold the correct amount of federal income tax from your periodic pension, annuity”.
Where this calculator stops
It prices the 2.2 formula on all service and tests the guides’ age and service combinations. It does not model the actuarial annuity alternative, the older pre-July 1998 percentages for Tier I members who did not upgrade (“If you do not upgrade service to the 2.2 formula, you are entitled to the following formula for service credit earned prior to July 1, 1998:” 1.67, 1.9, 2.1 and 2.3 percent bands), the 2.2 upgrade cost, the 20 percent cap on yearly salary increases, the Rule of 85 for state agency employees, the single-sum benefit for members with under five years, the Tier II salary limit, post-retirement employment limits, or cost-of-living increases. A Tier I member with pre-1998 service who did not buy the upgrade should use the TRS estimate, because this page would overstate the annuity.
How it was checked: a second, independent engine (exact fractions, the percentage, maximum and age conditions read from the archived guide text) agreed with this page’s engine on 120,000 random combinations of tier, service, age and salary, and the shipped script was driven in a browser on a grid of cases against both. The rules were read from Chapter 9 of the TRS Tier I and Tier II member guides.
Common mistakes
- Using your latest salary. Tier I averages the four highest years within the last 10; Tier II averages the eight highest within the last 10.
- Using the Tier I ages for a Tier II member. Tier II needs age 67 with 10 years for an unreduced annuity.
- Assuming 2.2% applies to all of your service. Tier I service before July 1998 uses lower percentages unless the 2.2 upgrade was bought.
- Expecting more than 75%. The annuity stops at 75% of final average salary, and Tier I rounds 74.6% and above up to it.
Related: TRS Illinois retirement decisions, public pension decisions by system, single life versus joint and survivor, and Illinois retirement taxes.
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Answer againSources
- Teachers’ Retirement System of Illinois, Tier I Member Guide, Chapter 9: Retirement Benefits: https://www.trsil.org/members/tier-i/guide/chapter-9-retirement-benefits
- Teachers’ Retirement System of Illinois, Tier II Member Guide, Chapter 9: Retirement Benefits: https://www.trsil.org/members/tier-ii/guide/chapter-9-retirement-benefits
- IRS, Topic no. 410, Pensions and annuities: https://www.irs.gov/taxtopics/tc410
- IRS, About Form W-4P, Withholding Certificate for Pension or Annuity Payments: https://www.irs.gov/forms-pubs/about-form-w-4p
Read from the system publications linked above on October 30, 2026. General information, not legal or tax advice, and not an estimate from the retirement system. Your own facts decide the outcome, and your retirement system, your plan administrator or a benefits advisor is the right place to confirm anything consequential.