federal courts-based on the PSI, the statute and the sentencing guidelines. age usually doesn't play a role
its based on
A) offense level which includes "relevant conduct" (for example if you are convicted of 3 bankrobberies but there is credible evidence you robbed 6 that can count)
B) criminal history-0 means you have no record, 2 means minor stuff-if you are up at 5 you've been a long time asshole.