This page explains the PERSI calculator. The rules it uses are explained in plain English on the benefit formula, early retirement and payment options pages.
- 1
Count your service
PERSI counts service in months. We add a month for each month from today to your start date (none if you've stopped working).
Member Handbook (2019), p. 10, Credited Service; Credited Service flyer - 2
Count your age
In whole months, up to the end of the month before your benefits start. The month you reach an age counts, so benefits can start the 1st of the month after you turn 55 or 65.
Member Handbook (2019), pp. 23-24; Early Retirement brochure (01/14) pp. 2-4; PERSI ACFR 2024 p. 8 - 3
Check eligibility
Vested (60 months) and at least 55. A full benefit at 65 or by the Rule of 90 (age + service in months).
Member Handbook (2019), pp. 23-24; Early Retirement brochure (01/14) pp. 2-4; PERSI ACFR 2024 p. 8 - 4
Apply the formula
Average monthly salary × 2% × months ÷ 12, capped at the average monthly salary. We use the average you enter.
Member Handbook (2019), p. 22; PERSI ACFR 2024 Summary of Plan Provisions, p. 8; PERSI FY2025 Financial Statements Note 1, p. 19 (2.0% for all members except police and fire) - 5
Cut for early retirement
The smaller of the time to 65 and the time short of 90, through PERSI's former Table A factors (3% a year for 5 years, then 5.75%).
Member Handbook (2019), p. 25; Early Retirement brochure (01/14) pp. 3-4; PERSI's former rule 544 Table A, page 4 (DLC on or after Oct. 1, 1994), Idaho Administrative Bulletin Vol. 23-11 (Nov. 1, 2023), Docket 59-0101-2301 - 6
Price the options
Options 1 and 2 with former Table C (by the age gap, rounded to the nearest year); Options 3, 4a and 4b add your Social Security estimate × former Table B (by the time to your Social Security full retirement age).
PERSI's former rule 544 Table C, page 3 (retiring on or after July 1, 2011), Admin. Bulletin Vol. 23-11; same table on HB p. 28 ('Amended 2-1-2011'); PERSI's former rule 544 Table B, pages 1-3, Admin. Bulletin Vol. 23-11; method on HB p. 29 (sample estimate) and Retirement Options brochure p. 7 - 7
Project the PAA
Only the 1% minimum, prorated 1/12 a month in the first year.
PERSI ACFR 2024 Summary of Plan Provisions, p. 9; PERSI FY2025 Financial Statements Note 1, p. 19; PAA FAQ web page; Member Handbook (2019), p. 52
What the calculator doesn't cover
- Your average monthly salary: we use what you enter. PERSI figures it from your pay history.
- Police and firefighter service, mixed service, and members whose last contribution was before October 1994 (older multipliers and factor tables).
- The minimum benefit, the IRS pay and benefit limits, and recalculation after a return to covered work.
- Purchase-of-service costs, which PERSI quotes.
- Disability benefits (we show PERSI's service rule only), the Choice 401(k) Plan and income tax.
How we check the math
The calculator runs on a small engine that reads every rule from one data file, with a source for each. Automated tests check it against every worked example in our PERSI sources. The tests run every time the site is built.
| Example | PERSI shows | Our engine |
|---|---|---|
| Handbook sample: Regular allowanceMember Handbook (2019), p. 29, sample retirement estimate (form RS120) | $1,350.46 | $1,350.46Match |
| Handbook sample: early factorMember Handbook (2019), p. 29, sample retirement estimate (form RS120) | 0.654 | 0.654Match |
| Handbook sample: Option 1Member Handbook (2019), p. 29, sample retirement estimate (form RS120) | $1,165.45 | $1,165.45Match |
| Handbook sample: Option 2 (annuitant)Member Handbook (2019), p. 29, sample retirement estimate (form RS120) | $629.32 | $629.32Match |
| Handbook sample: Option 3, thenMember Handbook (2019), p. 29, sample retirement estimate (form RS120) | $1,926.46 / $426.46 | $1,926.46 / $426.46Match |
| Handbook sample: Option 4b, then (annuitant)Member Handbook (2019), p. 29, sample retirement estimate (form RS120) | $917.32 / $167.32 | $917.32 / $167.32Match |
| Options brochure (2011): early factorRetirement Options brochure (01/14) p. 7, estimate dated May 21, 2011 | 0.850 | 0.850Match |
| Options brochure (2011): Option 4b, thenRetirement Options brochure (01/14) p. 7, estimate dated May 21, 2011 | $1,720 / $422 | $1,720 / $422Match |
| Handbook comparison chart: Option 3Member Handbook (2019), p. 30, comparison of options (member 55, CA 54, Social Security $1,200, Regular $1,000) | $1,541 | $1,541Match |
| Early Retirement brochure: monthly benefitEarly Retirement brochure (01/14) p. 5 (image) | $818.60 | $818.60Match |
| Reduction table, 1 to 10 yearsMember Handbook (2019), p. 25, reduction table for DLC on or after Oct. 1, 1994 | 10 rows | 10 matchMatch |
| 2026 PAA multipliers2026 PAA Follow-Up (Mar. 3, 2026), multiplier table | 13 rows | 13 matchMatch |
| Disability service at 50 with 120 monthsDisability flyer (Nov. 2021); Member Handbook (2019), pp. 35-37, 61 (glossary example: 120 months at age 50 plus 180 projected months = 300 months) | 300 months | 300 monthsMatch |
The options brochure and the handbook's comparison chart round to whole dollars; we compare in whole dollars.
What to check with PERSI
These points aren't settled by the sources. Each is labeled "Check with PERSI" wherever it appears.
Docket 59-0101-2301 deleted rule 544 (Tables A, B and C) effective July 1, 2024, and the current IDAPA rules print no factors, yet HB says factors are set by rule. The engine uses the deleted tables; PERSI may now use different factors.
We use the factor tables from PERSI's former rule 544, which reproduce PERSI's own sample estimates. Every option amount and early cut on this site carries this label.
What would settle it: A current PERSI factor table or a 2025-2026 RS120 estimate from PERSI.
The engine counts age to the end of the month before retirement (derived from two worked examples). No source states the method in words.
We count your age in whole months up to the end of the month before your benefits start, so the month you reach an age counts as reached.
What would settle it: PERSI's written method, or an estimate for a member born on the 1st of a month.
Two examples fit rounding to the nearest year (4 months to 0, 9 months to 1); a 6-month difference is not covered.
We round the age gap between you and your contingent annuitant to the nearest whole year (6 months rounds up).
What would settle it: PERSI's method or an estimate with a 6-month age difference.
Sources disagree between the 42-month average, the 36-month average and a 3-year average.
We cap the estimate at the average monthly salary you enter (the 42-month average). Few teachers come near the cap.
What would settle it: Idaho Code 59-1342 text (could not be downloaded).
The ACFR gives $30.29 per year of service without saying monthly or annual; the engine does not apply it.
We don't apply the minimum benefit; it only matters for very small pensions.
What would settle it: Idaho Code 59-1342 text or a PERSI publication stating the period.
legislature.idaho.gov dropped the connection; statute numbers are as PERSI quotes them.
We quote Idaho Code section numbers as PERSI's own publications give them.
What would settle it: The user downloading the sections listed in DOWNLOADS.md.
The newest Member Handbook found is the July 2019 revision; options and early-retirement brochures are dated 01/14.
We use the 2019 handbook for rules that newer PERSI flyers, web pages and financial reports don't change, and the newer source where they do.
What would settle it: A newer handbook from PERSI, if one exists.
Known only from PERSI's web page summary; the bill text was not downloaded.
We repeat PERSI's web page summary and label it.
What would settle it: SB 1276 (2026) as enacted.
Only the 1% mandatory PAA is assured, and only when the CPI-U rises 1% or more; Board increases are discretionary.
Our projections assume only the 1% minimum PAA. Anything more is up to the PERSI Board and the Legislature.
What would settle it: Nothing; projections stay labeled as estimates.
Where PERSI's sources disagree
- Benefit maximum. The handbook p. 22 caps the benefit at the highest 42-month average salary; IDAPA 59.01.01.527 says 36 consecutive months; the purchase flyer and the handbook p. 47 say the 3-year average. Member Handbook (2019), p. 22; IDAPA 59.01.01.527; Purchasing Base Plan Service flyer, Purchase Limits; Member Handbook (2019), p. 47
- 90-day rule employer. The handbook (2019) describes the early-retiree 90-day rule for the same employer; the Oct. 2022 flyer quotes 59-1356(1) as any employer participating in PERSI. The newer flyer is used. Member Handbook (2019), p. 34 (2019); Working After Retirement flyer (Oct. 2022), quoting Idaho Code 59-1356(1)
- Option factors. The handbook p. 30's illustration ($800/$894 for a 1-year-older member) uses the pre-July 2011 factors, while the handbook p. 28 prints the 2011 table (.848/.926). Member Handbook (2019), pp. 28, 30; PERSI's former rule 544 Table C
- Rule name. The handbook p. 24's Doug example says 'Rule of 90' where the arithmetic is the Rule of 80 (police). Member Handbook (2019), p. 24
- Option 3 percent. The handbook p. 29 prints 22.10% for the post-SSFRA share; 426.46/1926.46 = 22.14%. Member Handbook (2019), p. 29
- PAA statute and dates. PAA notices cite '§56-1355' (59-1355 meant); the 2026 retro table's last row ends '2/28/2027' (2022 meant). 2025 PAA notice (Dec. 30, 2025); 2026 PAA Follow-Up (Mar. 3, 2026)
- PAA minimum. The handbook p. 52 describes the PAA as up to the CPI or 6% without the 1% mandatory minimum; ACFR 2024 and FS2025 describe the 1% mandatory PAA. Member Handbook (2019), p. 52; PERSI ACFR 2024 p. 9; PERSI FY2025 Financial Statements Note 1, p. 19
- Table A rounding. The handbook p. 25 prints 32.25% for 8 years early ($1,000 becomes $677.50); former rule 544 Table A prints .677 for 8 years 0 months (and .792 for 6 years, .562 for 10 years, each 0.0005 below the exact percent). PERSI's own estimate on the handbook p. 29 uses the table factor (.654), so the engine uses the table. Member Handbook (2019), p. 25; PERSI's former rule 544 Table A
- Retirement Options brochure factors. The brochure's sample estimate (run May 21, 2011, for a June 1, 2013 retirement) uses the pre-July 2011 Table C factors (.835/.915). Under the July 1, 2011 table a member 1 year younger than the CA gets .875/.938. The brochure is an illustration only; current estimates use current factors. Retirement Options brochure (01/14) p. 7; PERSI's former rule 544 Table C
Sources
- PERSI Member Handbook (Handbook revision July 2019)
- PERSI Annual Comprehensive Financial Report, FY ended June 30, 2024 (FY2024)
- PERSI Financial Statements, FY ended June 30, 2025 (October 2025)
- Retirement Options brochure (01/14 (2014 law))
- Early Retirement brochure (01/14 (2014 law))
- PERSI Benefits at a Glance (Feb. 2019)
- Idaho Administrative Bulletin Vol. 23-11, pp. 119-153 (Docket 59-0101-2301, former rule 544 Tables A, B and C) (Nov. 1, 2023)
- IDAPA 59.01.01, Rules of the Public Employee Retirement System of Idaho (Effective July 1, 2024)
- 2025 Postretirement Allowance Adjustment notice (Dec. 30, 2025)
- 2026 PAA Follow-Up (Mar. 3, 2026)
- Contribution Rates web page (saved Nov. 12, 2026)
- Working After Retirement flyer (Oct. 2022)
- Certified Instructional Staff or Pupil Service Staff: Return to Work flyer (June 2019)
- Working After Retirement web page (saved Nov. 12, 2026)
- Death Benefits flyer (Nov. 2021)
- Withdrawing Funds flyer (Nov. 2021)
- Disability flyer (Nov. 2021)
- Purchasing Base Plan Service flyer (undated)
- Using Sick Leave: School District Retirees flyer (undated)
- PERSI Plan Comparison Chart (01/07/2026)
- PERSI Choice 401(k) Plan Summary Plan Description (2023)
- PERSI Taxes / 1099-R web page (saved Nov. 12, 2026)
- PERSI employer newsletter (March 2026)
- PERSI employer newsletter (July 2026)
- Idaho State Tax Commission, Idaho Retirement Benefits Deduction (saved Nov. 12, 2026)
Idaho Code sections are quoted as PERSI's publications give them; the Idaho Legislature's site couldn't be downloaded for this review.
Source: PERSI Member Handbook, Handbook revision July 2019, pp. 10, 22, 23-24, 25, 29, 30, 35-37, 52, 61. Also: PERSI Credited Service flyer; Early Retirement brochure (01/14); PERSI ACFR (FY2024); PERSI Financial Statements (FY2025); Idaho Administrative Bulletin, Nov. 1, 2023 (former rule 544); Retirement Options brochure (01/14); PERSI PAA notices and web page; PERSI Disability flyer (Nov. 2021). Last reviewed .