How Do You Know What Your Tax Bracket Is?

Joyce, i'm 65. Just turned 65 in july of this year. It's medicare time for you. Are you im entitled to a social security or a pension? No pension. But i am entitled to such security, which i'm not taking as yet. Y next year, i'll take that. So nice to talk to you. I am confused on withdrawals. But mostly because all of my income is from stock, e t f and bond, e tf and some cash, i don't know how to figure out ahead of time what my tax bracket is,. so that i can go ahead and withdraw some money but stay within my tax bracket.