Things You'll Need
National wage indexing series
Collect all of your annual earnings statements that were taxed by social security. This is listed in your social security statement.
Multiply each year's taxable earnings by the national wage indexing factor for that year. This factor can be found from the Social Security Administration website.
Add up your annual earnings adjusted to the national average wage index from the time you turned 21 to the time of your disability.
Divide that total by the number of years you have worked past the age of 21.
Divide by 12 and round down to the full dollar amount. This result is your Average Indexed Monthly Earnings or AIME.
Determine your primary insurance amount or PIA. The PIA is comprised of three percentages, or bend points, based on your AIME. For 2010, the first bend point is $761, the second is your AIME
between $761 and $4,586, and the third is your AIME above $4,586. If your AIME is less than $4,586, subtract $761. If your AIME is above $4,586, subtract $4,586.
Take 90% of your AIME for your first $761. If your AIME is $761 or less, this figure is your estimated monthly social security disability wage. If your AIME is above $761, this figure is $684.90. This is your first portion.
Take 32 percent of your AIME between $761 and $4,586. If your AIME is above $761, but below $4,586, subtract $761 from your AIME and multiply by 32 percent. If your AIME is above $4,586, this figure is $1,224. This is your second portion.
Take 15 percent of your AIME above $4,586. If your AIME is above $4,586, subtract $4,586 and multiply by 15 percent. This is third portion.
Add the three portions together. The total is your expected monthly social security benefit.