The Minimum: Age 55
CalSTRS members can begin service retirement as early as age 55, provided they have at least five years of service credit. That is the legal floor. It is rarely the financially optimal answer.
Retiring at the minimum age means retiring at or near the lowest point on your age factor scale, which permanently reduces your monthly pension for the rest of your life. There is no do-over. Once your benefit is set at retirement, that age factor is locked in.
The "Full" Age: 60 or 62, Depending on Your Tier
Your age factor reaches its base rate, 2%, at age 60 if you are under the CalSTRS 2% at 60 formula, or age 62 if you are under 2% at 62. Waiting past that point continues to increase your age factor up to a maximum reached at 63 (2% at 60) or 65 (2% at 62).
Retiring Based on Years of Service
Some CalSTRS members qualify to retire before age 55 with enough years of service credit, though this depends on your specific plan provisions and is less common. For most teachers, the meaningful early-exit question is not "can I retire" but "what does retiring early actually cost me in reduced monthly income, for the rest of my life."
The Question That Actually Matters
"When can I retire" and "when should I retire" are different questions with different answers. The first is a CalSTRS eligibility rule. The second depends on your age factor, your final compensation trajectory, your 403(b) balance, whether you have Social Security credits, your spouse's situation, and your health.
We walk through all of that in a free assessment rather than trying to answer it in the abstract, because the honest answer is different for every teacher.