Purchasing service credits can raise your WA DRS pension for the rest of your life, but it also means writing a real check today. Before deciding if it is worth it, you need to know exactly how the math works: what it costs, how long it takes to break even, and what your actual rate of return looks like. Here is the full calculation, step by step, using a worked TRS Plan 3 example.
Before You Start: The Three Numbers You Need
To run this calculation for yourself, you need three pieces of information: your plan’s benefit formula percentage, the number of service credit years you want to purchase, and your average final salary on a monthly basis. For this example, we will use TRS Plan 3, which credits 1% of your average final salary for every year of service, and we will assume the maximum purchase of 5 years, or 60 months.
Step 1: Calculate Your Monthly Benefit Increase
Multiply your plan’s benefit percentage by the number of years you are purchasing, then multiply that by your monthly average final salary. Say your salary works out to $60,000 a year, or $5,000 a month.
| Calculation | Result |
|---|---|
| 1% x 5 years | 5% |
| 5% x $5,000 monthly salary | $250 monthly benefit increase |
Purchasing 5 service credit years in this example would raise your monthly pension benefit by $250 for the rest of your life, once you retire.
Step 2: Find the Purchase Cost
Now for the cost. Take your new monthly benefit amount and divide it by an “administrative factor” that corresponds to your age at the time of purchase. You can find this factor on the DRS website’s administrative factors table. TRS 2 and TRS 3 share one table, while PERS and SERS each use their own separate tables with different numbers, so make sure you are pulling the correct one for your specific plan.
For this example, let’s say you are 62 years old at the time of purchase, and the administrative factor at that age happens to be 0.054416.
| Calculation | Result |
|---|---|
| $250 monthly benefit ÷ 0.054416 administrative factor | $45,942 purchase cost |
In this example, purchasing 5 service credit years at age 62 would cost roughly $45,942 to increase your monthly pension by $250. This is important: administrative factors are updated annually by DRS and change based on your exact age at purchase, so always pull the current table for your plan rather than relying on an old number. Treat the figure above as an illustration of the process, not a live rate.
Step 3: Calculate Your Break-Even Point
Next, figure out how long it will take for the extra monthly pension payments to pay back what you spent. Divide your purchase cost by your monthly benefit increase.
| Calculation | Result |
|---|---|
| $45,942 ÷ $250 monthly increase | 183.8 months |
| 183.8 months | About 15.3 years |
In this example, it would take about 15.3 years of collecting your pension before the extra monthly payments fully repay the $45,942 you spent. Every month you collect beyond that break-even point is pure upside on your original investment.
Step 4: Calculate Your Rate of Return
Finally, turn this into an annualized rate of return so you can compare it to other investment options. Multiply your monthly benefit increase by 12 to get an annual figure, then divide that by your original purchase cost.
| Calculation | Result |
|---|---|
| $250 x 12 months | $3,000 annual benefit increase |
| $3,000 ÷ $45,942 purchase cost | 6.53% annualized rate of return |
A 6.53% guaranteed annual return is a strong number, especially compared to what you can typically find in savings accounts, CDs, or bonds. And that return keeps compounding in your favor the longer you live to collect it, since a pension is guaranteed for life rather than a fixed payout period.
Why Age at Purchase Changes Everything
Administrative factors are built around life expectancy. The younger you are at the time of purchase, the longer DRS expects to be paying you that extra benefit, which typically makes the same purchase more expensive at a younger age and less expensive as you get closer to retirement. Let’s compare our age 62 example to what the same purchase might look like at age 55, using a smaller illustrative administrative factor of 0.04.
| Age at Purchase | Administrative Factor | Purchase Cost | Break-Even |
|---|---|---|---|
| 55 (illustrative) | 0.04000 | $62,500 | About 20.8 years |
| 62 (from earlier example) | 0.05442 | $45,942 | About 15.3 years |
Notice that purchasing later, closer to when you plan to actually retire, tends to cost less and break even faster in this simplified comparison. That is because DRS is factoring in a shorter expected payout period. This is exactly why it is worth running the calculation at your specific age rather than assuming the numbers will look the same at every stage of your career.
Is Buying Service Credits Right for You?
The math above shows why this can be an attractive move, but a few personal factors matter just as much as the calculation itself.
- Do you have the lump sum available? This is typically a one-time payment, so you need the cash on hand or a way to fund it without derailing other savings goals.
- How long do you expect to collect your pension? The break-even period only pays off if you live long enough past it. Family health history and your own health are worth factoring in.
- What else could that money do for you? Compare the guaranteed rate of return against other places that same lump sum could go, keeping in mind that a pension increase is guaranteed and does not carry market risk.
- Your age at purchase matters. Administrative factors change with age, so running this calculation at different ages can show whether purchasing sooner or later makes a bigger difference for your specific numbers.
None of these four factors has a universally right answer. A 6.53% guaranteed return might be an easy yes for someone with a healthy emergency fund and a family history of longevity, and a harder call for someone who would need to dip into savings earmarked for something else. Running the actual numbers, rather than relying on a rule of thumb, is what turns this from a guess into an informed decision.
Common Mistakes to Avoid
- Using an outdated administrative factor. Since these tables update every year, a calculation done with last year’s numbers can be noticeably off from what you would actually pay today.
- Comparing across the wrong table. TRS 2 and TRS 3 share a table, but PERS and SERS each use their own. Pulling a number from the wrong plan’s table will throw off your entire calculation.
- Ignoring your own life expectancy. The break-even period is only meaningful if you actually expect to collect your pension well past that point. Be honest with yourself about your health and family history when weighing this decision.
- Draining savings you need elsewhere. A service credit purchase is usually a lump sum. Make sure funding it does not leave you short on your emergency fund or other near-term goals.
Since the exact administrative factor, break-even period, and rate of return will all be different for your own age, plan, and salary, it is worth running your own numbers before committing to a purchase. You can schedule a personal meeting and we will walk through your specific service credit purchase calculation together.
Frequently Asked Questions
Where do I find my plan’s administrative factor?
DRS publishes administrative factor tables on their website. TRS 2 and TRS 3 share a table, while PERS and SERS each have their own. Since these factors update annually, always use the current table rather than an old figure.
How many service credit years can I purchase?
In the example used here, the maximum purchase was 5 years, or 60 months. Your own plan’s maximum may differ, so confirm the limit that applies to your specific situation with DRS.
What is a good rate of return for a service credit purchase?
There is no universal answer, but a guaranteed return in the mid-single digits, like the 6.53% shown in this example, is generally considered attractive compared to low-risk alternatives like savings accounts, CDs, or bonds.
Does my age affect the cost of purchasing service credits?
Yes. The administrative factor used in the cost calculation is tied to your exact age at the time of purchase, so the same benefit increase can cost a different amount depending on when you buy it.
Is purchasing service credits a guaranteed investment?
The resulting increase to your monthly pension benefit is guaranteed for life once you retire, which is what makes the calculated rate of return attractive compared to market-based investments that carry risk.
Is it cheaper to buy service credits earlier or later in my career?
In general, purchasing closer to your actual retirement age tends to cost less per dollar of benefit increase, since the administrative factor accounts for a shorter expected payout period. That said, the right timing still depends on your own cash flow and when you have the lump sum available.
Can I run this calculation myself before meeting with anyone?
Yes. All you need is your plan’s benefit percentage, the number of years you want to purchase, your average final salary, and the current administrative factor for your age and plan from the DRS website. The four-step process shown here works the same way regardless of your specific numbers.
What counts as service credit that I might be able to purchase?
This typically covers gaps like an authorized leave of absence, or in some cases prior public service, though the specific categories DRS allows you to purchase can vary. Check with DRS directly to confirm which type of service credit applies to your own work history.
P.S. If you found this walkthrough helpful and want more videos like this on WA DRS pension math, come join a community of over 150 members working through these exact decisions together, with free courses and resources included.
