It depends.
Your tier I benefits are treated the same as Social Security benefits. So, depending on your total income, the percentage that is taxable will vary.
Your tier II and vest interest benefits are fully taxable for federal tax purposes.
Your tax rate will also vary depending on your total income.
To determine the federal withholding you should request, follow this link:
https://www.rrb.gov/sites/default/files/2018-05/TXB-25%20%2804-18%29%20%28Internet%29.pdf
For more information about your railroad retirement benefits, follow this link:
Railroad Retirement Taxes
