In the GS system, pay is based on three factors:
Grades run from 1 to 15 with 15 receiving the highest pay. Your grade is based on education, experience, and position. Some positions are limited in terms of what grade they can be paid at. Also grades have minimum educational and experience requirements to qualify for the grade. Grade increases are considered a promotion even though your title may not change. Each grade increase equates to a 10-15% pay increase.
Step is based on how long you have worked for the federal government. Steps run from 1 to 10 with step 10 receiving the highest pay. Employees start at step 1 and move to step 2 after 1 year of service. As you move up in step the time intervals between step increases become longer. It takes 18 years of service to reach step 10. Each step increase equates to a 2-3% increase in pay.
The final factor used to determine pay on the GS pay schedule is location. There are 34 different pay localities across the US. Each locality adds a different percentage to your base pay. Locality is designed to accommodate for higher costs of living in and around major cities. Locality rates are based on where you work, not where you live. If you do not work in or around a major metropolis you will fall under the “Rest of U.S.” locality area.
Click on this link for a GS pay calculator. This will estimate your base pay and includes locality. You will need to know the GS grade and step of the position and the county of the installation you are applying at; https://www.federalpay.org/gs/calculator