Social Security Society benefits are based upon what you have paid into the Social Security system in taxes. Each year, when you file your tax return, you report how much money you earned. The amount of money you receive depends upon the amount of money you have paid in.
One way to determine how much you monthly benefit would be if you applied and were approved for Social Security Disability would be to review your annual Social Security Statement. These are mailed each year by the Social Security Administration.
Another way to find out your benefit amount is to view Social Security's Estimator on the SSA website. Just follow this link: http://www.socialsecurity.gov/estimator/
While the Estimator may not be accurate to the penny, it will give you an idea of what your monthly benefit would be for the different types of monthly payments offered by Social Security (i.e., Social Security Disability, Old-Age/Retirement, etc.).