From the article: "...FERS also uses the high-3 average, paying 1 to 1.1 percent of the high-3 average salary for each year of service. Under FERS, a postal worker with a high-3 average of around $60,000 and 20 years of service earns $1,007 a month without any deductions. That equals about $12,000 annually. A worker with the same salary and 40 years of service earns $2,013 monthly, or about $24,000 annually. However, FERS employees also receive Social Security benefits and distribution of their TSP payments, so this number is actually higher..."
Article Reference: work.chron.com