Updated October 30, 2026. Quick answer: The Illinois Municipal Retirement Fund Regular Plan pays 1-2/3% of your final rate of earnings (FRE) for each of your first 15 years of service credit and 2% for each year after, up to a 75% maximum. Tier 1 members can start at 55 with 8 years and have a full pension at 60; Tier 2 members start at 62 with 10 years and have a full pension at 67. Computed for a Tier 1 member with 30 years and a $60,000 FRE retiring at 60, that is $33,000 a year (computed), or $2,750 a month (computed). Enter your own numbers below; the figure is the pension before any option, before the 13th payment and before the annual increases.
Calculate your IMRF Regular Plan pension
This page applies the IMRF Regular Plan formula to your tier, service credit, age and final rate of earnings. It runs on this page and sends nothing anywhere. It covers the Regular Plan only, not the SLEP or ECO plans. IMRF puts the tier cut-off at “Before January 1, 2011, you are in Tier 1” and “On or after January 1, 2011, you are in Tier 2” for the Regular Plan.
For a decision, use IMRF’s own estimator: “Use the Pension Estimator in your Member Access account to create your own pension estimates.” Start at imrf.org. This page is the published formula, shown so you can see the arithmetic.
The formula, as IMRF prints it
IMRF prints the same formula for both tiers: “1-2/3% of your FRE for each of the first 15 years of service credit, plus” “2% of your FRE for each additional year of service credit over 15 years.” The cap is “Your total pension at retirement cannot exceed 75% of your final rate of earnings.” Service credit counts “in years and months”.
The FRE differs by tier. Tier 1: “your highest total earnings during any 48 consecutive months within your last 10 years of IMRF service, divided by 48”. Tier 2: “your highest total earnings during any 96 consecutive months within your last 10 years of IMRF service, divided by 96”. Either tier uses a lifetime average instead if it gives the larger pension. Tier 2 also caps the earnings that count: “Under Tier 2, a member’s wages are capped at $129,192.26 in 2026.” The cap is indexed each year, so a Tier 2 FRE is already built from capped earnings; enter the capped figure, not your gross pay.
Worked example, calculated for Tier 1: the first 15 years at 1-2/3% is 25% and the next 15 years at 2% is 30%, so 30 years is 55% of a $60,000 FRE = $33,000 a year (computed), $2,750 a month (computed). The pension reaches the 75% maximum at 40 years (25% + 25 x 2%).
When the pension is not reduced
Tier 1: “Must have at least eight years of service credit” and “Must be at least age 55.” IMRF says “At age 60 or later” with eight years is unreduced, and so is “At age 55 or later” with 35 years. Tier 2: “Must have at least 10 years of service credit” and “Must be at least age 62.” Unreduced is “At age 67 or later” with 10 years, or “At age 62 or later” with 35 years.
Retiring early: the reductions, computed
Tier 1 with fewer than 30 years is reduced “1/4% for each month you are under age 60”. Tier 2 with fewer than 30 years is reduced “1/2% for each month you are under age 67”. With at least 30 but fewer than 35 years, both tiers apply the lesser of two reductions: “1/4% for each month of service credit less than 35 years” in Tier 1, and “1/2% for each month of service credit less than 35 years” in Tier 2.
Worked example, calculated for Tier 1: 25 years is 25% + 20% = 45% of a $60,000 FRE = $27,000 a year (computed) before the reduction. At 56 the member is 48 months under 60, so the reduction is 48 x 1/4% = 12% and the pension is $23,760 a year (computed), $1,980 a month (computed). Calculated for Tier 2 with 32 years at 62: 25% + 17 x 2% = 59% of $60,000 = $35,400 a year (computed) before the reduction. The member is 60 months under 67 (30%) but 36 months under 35 years of service (18%); the lesser applies, so the pension is $29,028 a year (computed), $2,419 a month (computed).
| Tier 2 age at retirement | Reduction | Annual pension | Monthly pension |
|---|---|---|---|
| 62 | 30.0% | $14,700 (computed) | $1,225 (computed) |
| 63 | 24.0% | $15,960 (computed) | $1,330 (computed) |
| 64 | 18.0% | $17,220 (computed) | $1,435 (computed) |
| 65 | 12.0% | $18,480 (computed) | $1,540 (computed) |
| 66 | 6.0% | $19,740 (computed) | $1,645 (computed) |
The table holds 20 years and a $60,000 FRE fixed and moves only the retirement age, in whole years; every row has fewer than 30 years, so the age rule is the one that applies.
What the pension does not decide
1. The pension option. The figure here is the maximum single-life pension. A survivor choice lowers it; the trade is explained on the single life versus joint and survivor page.
2. After you retire. IMRF adds yearly increases and a 13th payment; the plan-level decisions are on the IMRF 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 Regular Plan formula and tests the stated age and service combinations. It does not model the SLEP or ECO plans, reciprocal service in another Illinois system, the rules for unused sick days, the cost of buying service (the pension buyback calculator covers purchases in general), disability or death benefits, the annual increases or the 13th payment. IMRF itself says unused sick days converted to service cannot meet the minimum-service tests, so enter only the service that counts toward them. The FRE is yours to enter: the page does not find your best 48 or 96 months.
How it was checked: a second, independent engine (exact fractions, the percentages, maximum, ages and service conditions read from the archived IMRF text) agreed with this page’s engine on 120,000 random combinations of tier, service, age and FRE, and the shipped script was driven in a browser on a grid of cases against both. The rules were read from the IMRF Tier 1 and Tier 2 Regular retirement benefit pages.
Common mistakes
- Using your final salary as the FRE. Tier 1 averages your best 48 consecutive months; Tier 2 your best 96, with earnings capped each year.
- Using the Tier 1 ages for a Tier 2 member. Tier 2 starts at 62 and is unreduced at 67.
- Assuming 2% applies from year one. The first 15 years earn 1-2/3% a year and only later years earn 2%.
- Expecting a full pension at 55 or 62 with fewer than 35 years. The 35-year route removes the age reduction; other members are reduced for the months under 60 or 67.
Related: IMRF retirement decisions, public pension decisions by system, single life versus joint and survivor, and Illinois retirement taxes.
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Answer againSources
- IMRF, Tier 1 Regular Retirement Benefits: https://www.imrf.org/en/members/inactive-members/tier-1-regular-retirement-benefits
- IMRF, Tier 2 Regular Retirement Benefits: https://www.imrf.org/en/members/inactive-members/tier-2-regular-retirement-benefits
- IMRF, Understanding Tiers and Plans: https://www.imrf.org/en/members/understanding-tiers-and-plans
- IMRF, Tier 2 Regular Plan: Your Contributions (2026 wage cap): https://www.imrf.org/en/members/tier-2-regular-plan/your-contributions
- 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.