Updated July 2026
What Is Uninsured and Underinsured Motorist Coverage Insurance?
Uninsured motorist coverage (UM) and underinsured motorist coverage (UIM) protect you when another driver causes a crash but can't pay for the damage. UM pays when the at-fault driver has zero insurance. UIM pays when they have insurance, but their liability limits fall short of your actual losses. Both coverages step in only after the other driver's insurance is exhausted or confirmed absent.
- A driver with no insurance rear-ends you at a stoplight. You have $8,000 in medical bills and $5,000 in vehicle damage. The at-fault driver has no liability coverage to pay your claim. Your uninsured motorist bodily injury coverage pays your medical bills up to your UM limit. Your uninsured motorist property damage coverage pays the vehicle repair costs, minus your deductible if your state requires one.
- A driver with California's minimum $15,000 bodily injury limit causes a crash that leaves you with $40,000 in medical expenses. Their liability insurance pays the $15,000 maximum. Your underinsured motorist coverage pays the remaining $25,000, up to your UIM limit. Without UIM, you would pay the $25,000 gap out of pocket or pursue a lawsuit against a driver unlikely to have recoverable assets.
- An unidentified driver sideswiping you on I-5 and fleeing counts as an uninsured motorist claim in California. You file a police report within 24 hours. Your UM coverage pays for your injuries and, if you carry UMPD, your vehicle damage. The coverage applies even though you never identified the other driver, as long as you meet your insurer's reporting requirements.
Who Needs Uninsured and Underinsured Motorist Coverage Insurance?
Carry this coverage if you live in a state with a high uninsured driver rate, commute in dense traffic where multi-car crashes are common, or cannot afford to pay medical bills out of pocket after a crash. It is essential if you carry liability-only insurance and have no collision or medical payments coverage to fall back on. Drivers with significant assets or high medical costs benefit most, as UM/UIM prevents a single uninsured driver from wiping out savings.
Match your UM/UIM limits to your liability limits. If you carry $100,000 in bodily injury liability, carry $100,000 in UM. The coverage costs little relative to liability, and mismatched limits leave you underprotected. If your state allows stacking and you insure multiple vehicles, calculate whether stacked limits justify the premium increase based on your household's total exposure.
How Much Does Uninsured and Underinsured Motorist Coverage Insurance Cost?
Adding uninsured and underinsured motorist coverage typically costs $8 to $18 per month, or $96 to $216 annually, depending on your selected limits and location.
- Your UM/UIM coverage limits—higher limits cost more, but mirror your liability limits in most cases.
- Whether you add uninsured motorist property damage (UMPD) or rely on collision coverage for vehicle repairs.
- Your ZIP code's uninsured driver rate—areas with higher uninsured percentages see higher UM premiums.
- Stacking rules in your state—stacked UM coverage, which multiplies limits across multiple vehicles, costs significantly more than non-stacked.
- Your claims history—prior UM claims can raise your premium at renewal, though less than at-fault liability claims.