1. Index your earnings. Each year's earnings are capped at that year's SS wage base, then multiplied by an indexing factor that scales historical wages to the national average wage level in the year you turn 60. Earnings after age 60 are not indexed (counted at face value).

2. Average the top 35 years (AIME). The 35 highest indexed-earnings years are summed and divided by 420 months. This is your Average Indexed Monthly Earnings. Fewer than 35 working years means $0 years drag the average down.

3. Apply the bend-point formula (PIA). The Primary Insurance Amount is 90% of AIME up to the first bend point, 32% between the two bend points, and 15% above the second. This is your benefit at full retirement age. The formula is deliberately progressive — lower earners get a higher replacement rate.

4. Adjust for claiming age. Claim before FRA and the benefit is reduced (about 6.7%/yr for the first 3 years, 5%/yr beyond). Claim after FRA and you earn delayed retirement credits of 8%/yr up to age 70. After 70 there is no further increase.

5. Break-even. Claiming later means fewer years of larger checks. The break-even age is where the cumulative total of the later claim overtakes the earlier one. Below that age the earlier claim is ahead; above it the later claim wins. Longevity is the deciding variable.

Caveats: This is a planning approximation. It uses current-law bend points and wage-base figures projected forward by your wage-growth assumption, simplified indexing, and does not model spousal/survivor benefits, the earnings test (if you claim early while still working), WEP/GPO, or taxation of benefits. Use the SSA statement figures for the authoritative PIA once available.