The insured usually has the option of choosing the dollar limits of your coverage. For the bodily injury portion that covers your injuries, consider matching the amount of your Bodily Injury Coverage. Some states give you no other option but to choose identical limits.
EXAMPLE:
If your limits of liability are $50,000 per person/$100,000 per accident, consider choosing the same limits for UMBI and UIMBI. If you are hit by an uninsured driver, each injured passenger (including the driver) can collect up to $50,000. If two passengers collect the full $50,000, then you reached your $100,000 maximum per accident.
Your UMPD limit is a different (and much easier) story. You can select a limit that closely mirrors the value of your vehicle. If your car is worth $20,000, and you do not carry Collision Coverage, then you should consider that much in UMPD coverage.