There are lots of variables involved in making the right decision for one's circumstances. Talking it over with a financial advisor - or a social security representative, if you don't don't have a financial advisor - is the best advice.
That said, there is an "easy" formula for calculating the break-even point, as you have posed the situation.
Let m be the number of months between early retirement and full retirement age.
Let r be percent of reduction for early retirement (it is not the same for everyone)
Let n be the number of months after full retirement age until break-even point
Then n = (1 - r)m / r
Note 1: The amount of the monthly benefit is irrelevant.
For example, if your full retirement age is 66.5 years and you retire at 62 then r = 27.5% = .275 and m = 54
That produces, n = (1 - .275)54/.275 = 142.36 months, which is about 11 years 10 months.. Your break even age would be 66 years 6 months + 11 years 10 months or 78 years 4 months.
Note 2: Unless you were born on the first of the month, the earliest you could draw social security is 62 years 1 month. That would change m to 53, r to 27.08%, and n would be 142.72 months.
Tom
