- Your monthly Base Plan benefit = your average monthly salary x 2% x your months of service / 12. For example, $2,038 x 2% = $40.76 a year of service; x 241 months / 12 = $818.60 a month.Member Handbook (2019), p. 22; Early Retirement brochure (01/14), p. 5 example
- The 2% multiplier applies if your last contribution was on or after July 1, 2000. Earlier dates used lower multipliers (1.667% to 1.917%).Member Handbook (2019), p. 22, history table
- Check with PERSIYour benefit cannot be more than your average salary. Check with PERSI: the handbook says the 42-month average, but the PERSI rules say the highest 36 consecutive months and the purchase flyer says the 3-year average.Three PERSI sources name different averages for the cap.Member Handbook (2019), p. 22; IDAPA 59.01.01.527; Purchasing Base Plan Service flyer
- Average monthly salary is the average of your highest 42 consecutive months of salary, for a last contribution on or after Oct. 1, 1994.Member Handbook (2019), p. 22
PERSI's example
PERSI's brochure shows $9,823.16 a year, $818.60 a month. Early Retirement brochure (01/14) p. 5 (image)
The handbook's sample estimate
What each year is worth
On a $5,000 average monthly salary, at a full benefit. Our engine's arithmetic.
| Years | Months | A month |
|---|---|---|
| 10 | 120 | $1,000 |
| 15 | 180 | $1,500 |
| 20 | 240 | $2,000 |
| 25 | 300 | $2,500 |
| 30 | 360 | $3,000 |
| 35 | 420 | $3,500 |
When the benefit is full
- You can retire with a full (unreduced) benefit at 65 with at least 5 years of service.Member Handbook (2019), p. 23; PERSI ACFR 2024 Summary of Plan Provisions, p. 8
- You can also retire unreduced before 65 under the Rule of 90: when your age plus your service add up to 90, you are at least 55 and you are vested. PERSI counts both in months, so each month you keep working adds two months toward 90.Member Handbook (2019), pp. 23-24; Early Retirement brochure (01/14), p. 4
- Benefits start on the first day of the month after the month you reach the age. If you turn 55 on May 15, you can retire June 1.Member Handbook (2019), p. 23
Before then, the benefit is cut for early retirement. See Early retirement.
If you last worked years ago
Your formula is the one in force on your date of last contribution. Earlier dates used shorter multipliers and longer averages. Member Handbook (2019), p. 22, table of base periods and general-member multipliers by date of last contribution (DLC)
| Last contribution | Average of | Multiplier |
|---|---|---|
| Through September 30, 1992 | 60 months | 1.667% |
| October 1, 1992 to September 30, 1993 | 54 months | 1.75% |
| October 1, 1993 to September 30, 1994 | 48 months | 1.833% |
| October 1, 1994 to June 30, 2000 | 42 months | 1.917% |
| July 1, 2000 or later | 42 months | 2% |
The benefit cap
Your starting benefit can't be more than your average salary. Member Handbook (2019), p. 22; IDAPA 59.01.01.527; Purchasing Base Plan Service flyer, Purchase Limits; Member Handbook (2019), p. 47
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. 47Sources 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 minimum benefit
Minimum benefit of $30.29 per year of credited service from March 1, 2024 ($29.99 before), not more than the accrued benefit. The ACFR does not say whether the figure is monthly or annual; the engine does not apply it. PERSI ACFR 2024 Summary of Plan Provisions, p. 8
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.
Try your own numbers in the calculator.
Questions
What is the PERSI formula?
Average monthly salary × 2% × months of service ÷ 12. Your average monthly salary is your highest 42 months in a row.
Is there a cap on a PERSI benefit?
Yes: the benefit can't be more than your average salary. PERSI's sources disagree on which average, but few teachers come near it.
Source: PERSI Member Handbook, Handbook revision July 2019, pp. 22, 23-24, 29, 47. Also: PERSI ACFR (FY2024); PERSI Financial Statements (FY2025); IDAPA 59.01.01; PERSI Purchasing Base Plan Service flyer; Early Retirement brochure (01/14); Idaho Code § 59-1341 (as PERSI quotes it). Last reviewed .