The formula, exactly as published

  1. Indexed earnings. Each year of your earnings is indexed to national average wage growth through the year you turn 60 (SSA’s AWI factors), capped at each year’s taxable maximum.
  2. AIME. Your highest 35 years are averaged into Average Indexed Monthly Earnings; missing years count as zero, exactly as SSA counts them.
  3. PIA. The 2026 bend points split your AIME into three bands credited at 90%, 32%, and 15% (SSA bend points). That is your primary insurance amount, with SSA’s rounding rules applied at each step, including the dime floor.
  4. Claiming adjustment. Five-ninths of 1% per month reduction for the first 36 months before full retirement age, five-twelfths beyond; 8% per year in delayed credits after FRA to 70; cost-of-living adjustments attach from 62 (reduction schedule). Month-of-birth edge cases follow SSA’s operating rules (POMS), down to claimants born on the 1st or 2nd of a month.

The same engine computes the earnings test, spousal top-ups, federal benefit taxation, Medicare IRMAA awareness, and required minimum distributions, each from its primary source: ssa.gov, IRS Publication 915, IRS Publication 590-B, and CMS’s premium schedule.

How we know it’s right

The engine ships with an automated verification battery: more than 90 tests that run before any release. The anchor: SSA publishes the maximum possible benefit for a worker retiring at 70 in 2026($5,181 a month). We reconstruct that worker (maximum taxable earnings every year since 1978), run the full chain, and require the engine to land on SSA’s figure. Around it: a battery of 27 personas across birth years and salaries checked for every invariant the rules imply, 39 adversarial edge-case vectors from an independent audit, and a golden snapshot that locks every output against silent drift. The web pages on this site use numbers exported from that same tested engine, including the free break-even calculator, whose math is pinned to the app engine’s outputs, number for number.

What we deliberately don’t compute

Survivor benefits, government-pension offsets, and disability conversions have edge cases we haven’t verified to our standard yet, so Whenwise says “we don’t compute this” in plain English instead of guessing. An estimate you can trust must be honest about its edges.

Freshness

SSA announces the next year’s values every October: COLA, bend points, wage base, earnings-test limits. Whenwise updates its rules bundle, re-runs the entire battery, and refreshes every number in the app and on this site. Estimates are educational, in today’s dollars, and your official amounts always come from SSA.