The early reduction
Section 404.410 says an old-age benefit is reduced when entitlement begins before the month you reach full retirement age. The reduction for the retired worker is 5/9 of 1 percent for each of the first 36 months, and 5/12 of 1 percent for each additional month. Thirty-six times 5/9 of 1 percent is 20 percent. Twenty-four more months at 5/12 of 1 percent is another 10 percent. Sixty months is a 30 percent reduction. A primary insurance amount of $1,000 becomes $700.00. Sixty months before full retirement age is age 62 only when full retirement age is 67. The form on this page caps the early box at 60 months and labels that case for a full retirement age of 67. Someone whose full retirement age is earlier than 67 has a shorter maximum reduction. The monthly factors are the same regulation. The age label is not universal.
The regulation's own illustration uses a different primary insurance amount and a different number of months, and it computes the reduction in dollars before it subtracts. This page applies the same percentages. On $1,000 and 60 months the result is an exact $700, so no rounding is visible. For other amounts the page drops a fraction of a dollar on the monthly benefit. The regulation's delayed-credit rule, described next, rounds the credit itself down to the next lower dime and can round the benefit down to the next lower dollar when a Medicare premium is involved. Those two procedures agree on the exact examples on this page. They can differ by less than a dollar on other amounts. Neither result is an award letter.
The delayed credit
Section 404.313 lets you earn a delayed retirement credit for each month from the month you reach full retirement age through the month you reach age 70. For a date of birth after January 1, 1943, the credit is 2/3 of 1 percent per month. That is 8 percent a year. Thirty-six months, the span from a full retirement age of 67 to age 70, is 24 percent. A $1,000 primary insurance amount becomes $1,240.00. The regulation multiplies the number of credits by that percentage, multiplies the result by the benefit, and rounds the increase to the next lower multiple of 10 cents before adding it. On $1,000 the 24 percent increase is an exact $240, so the dime rule does not change it.
Credits stop at age 70. The section says the earning period ends with the month you attain age 70. This page therefore stops the delayed box at 36 months when it is describing a full retirement age of 67. It does not add credits past that age. The percentage for a birth date on or before January 1, 1943 is smaller, and the regulation prints a table of those older percentages. This page uses only the "after January 1, 1943" row. If that is not your row, the 8 percent a year figure is the wrong credit.
The break-even month is arithmetic
The form compares the reduced benefit with the benefit at full retirement age, which for a $1,000 primary insurance amount is $1,000.00, starting 60 months later. The later benefit has to catch up both its own larger checks and the checks the earlier claim already received. The month from the earlier start is the later monthly amount times the months between the starts, divided by the difference in the monthly amounts. One thousand dollars times 60, divided by $300, is 200 months from the earlier start, which is 140 months after the later one begins. That 200 is not a figure the Social Security Administration publishes. It is what those two constant monthly amounts imply. Change the primary insurance amount and the month count changes only if the two benefits stop being a 30 percent reduction of the same starting amount. With a constant percentage, the break-even month does not depend on whether the primary insurance amount is $1,000 or $2,000. The dollar totals do.
A comparison of $700 and $1,240 is a different pair, 60 months of early claiming against 36 months of delay, and the gap between the start dates is longer than 60 months. The form's break-even line uses the early benefit and the delayed benefit you actually entered, and the months between those two start dates. If the delayed box is zero, the later benefit is the full-retirement-age amount. If you type months in both boxes, read the result as the catch-up between those two choices, not as a third official age.
What the comparison leaves out
Cost-of-living adjustments would raise both benefits after they start. The earnings test can withhold checks before full retirement age. Benefits can be taxable. A spouse or a survivor can be entitled on the same record, and the claiming age can change that entitlement. Medicare premiums can be deducted from the check. None of those is in the 200-month arithmetic. Living longer than the break-even month is not something this page knows. The month is a comparison of cash already assumed, not a prediction.
The primary insurance amount has to come from you: a Social Security statement, or a figure you are willing to test. This page will not build one from earnings. The retirement projection grows savings at a rate you type. It is not a benefit. The paycheck page stops Social Security tax at the annual wage base. Paying that tax is not the same as computing a retirement check. The official eCFR host did not return these two sections from the network used to check sources. The text cited here is the Legal Information Institute's copy of 20 CFR 404.410 and 404.313, which did return the regulation, including the 5/9 and 5/12 reduction and the 2/3 of 1 percent credit after January 1, 1943.
Giuseppe Ilarda, the site owner, writes and checks those factors. The disclaimer applies. Filing a claim, suspending a benefit, or choosing an age is a decision for you and, if you want it, for the Social Security Administration. This page does not file anything.