How the amount is worked out

The base figure and the revision rate

The amount is art. 27’s statutory base of ¥780,900 a year, multiplied by a “revision rate” (改定率) reset each fiscal year.

That ¥780,900 figure is not itself the amount paid. The current fiscal year’s revision rate — and so the actual payable amount — is not stated in the articles this site cites. The government publishes the rate each fiscal year.

Scaled by insured months

The base figure is scaled by the proportion of months you paid contributions for. The full rate requires 480 months (40 years) of insurance; the minimum to receive anything at all is 120 months (10 years). Months you actually paid contributions for count at full weight; months you were exempted count at a lesser weight under a four-tier schedule the Act sets, never zero. The detailed cascading arithmetic behind those four tiers is not covered on this site.

The deferral increase

Choosing to defer claiming from age 66 up to age 75 adds 0.7% to the base figure per month deferred, capped at 120 months (10 years) — a maximum increase of 84% at the full 10-year deferral (附則 art. 28 + Enforcement Order art. 4-5). See claiming early or deferring for the detail.

Revised every fiscal year

The revision rate is reset from the April payment each fiscal year (art. 27-2). In ordinary years it tracks wage growth measured over the preceding 12 months. Some years carry a more complex demographic adjustment on top; this site describes only the ordinary-years mechanism, in brief.

There is no separate revaluation step for past wages in this formula: the amount is scaled by a count of insured months, and there is no wage record to restate.

Floor and ceiling

No minimum pension distinct from the ordinary pro-rata formula was found.

No maximum amount on the pension itself was found. The month-count pro-rata does cap at 480 months, but that is a cap on the INPUT used to calculate the amount, not a stated ceiling on the pension itself.