I've run the numbers before. I didn't want to download it now but I believe I built my own calculator using the quick as well as detailed calculator form the SSA website.

https://www.ssa.gov/OACT/anypia/anypia.htmlThe main points I would highlight about the calculation is as follows (info as of 2015):

You SSA eleigilble earnings are your highest 35 years of wage history. The wages are adjusted for inflation. But the really important part to understand is how the bend points work and how drastically they reduce incremental benefits.

A quick simple way to estimate your benefits is to take your inflation adjusted top earnings years add them all together (If you have more than 35 years only include the top 35). Now divide them by 420 (35 years x 12 months) which gives you your average monthly earning history.

The first $856 of earnings history will generate 90% SS benefit or $770.

$857-$5,157 pays 32% benefits or $1,376.

Above $5,157 pays 15% benefits.

Things to keep in mind. 1) Earnings above the SS cap don't count and 2) the inflation factor published by the SSA will be most accurate for adjusting your historical earnings.

What I learned is that once your average annual salary from 35 years (including zeros for the non working early retired years) exceeds $62k you hit the 3rd bend point and see very little increase in SS benefits. I've personally worked far less than the 35 years and if I early retire when I anticipate I will be very close to that 2nd bend point.

ETA: Another way to think about it is that at $62K in average salary earnings you will receive a monthly benefit at Full Retirement Age (FRA) of about $2.1K. The earnings cap on SS is nearly twice that so if you made $120K a year for a full 35 years you benefit would only be $2.6K. So more than doubling your SS wages (and taxes paid) after the 2nd bend point only nets you about a $500 increase in monthly benefit or 24%.