Stacked vs. Unstacked Car Insurance

The main difference between stacked and unstacked insurance is how much uninsured motorist (UM) bodily injury coverage you can access after an accident. Stacked insurance lets you combine UM coverage limits across vehicles or policies for more protection, but it usually comes with higher premiums. Unstacked insurance limits you to the coverage amount for the vehicle involved in the crash.

There are two main types of insurance stacking: stacking within one policy and stacking across multiple policies, also known as vertical and horizontal stacking, respectively. Some states only allow one type of stacking but not the other, and some states don’t allow stacking at all, so it’s important to explore which options are available to you.

Also called interpolicy stacking, this method lets you combine uninsured motorist (UM) bodily injury coverage from multiple auto insurance policies. Your name must be listed on each policy, and they must be issued by the same insurer.

For example, if you have $35,000 in UM coverage on your own policy and you're also listed on a parent’s policy with $25,000 in coverage, you could stack those for a total of $60,000 in protection against an uninsured driver.

Also known as intrapolicy stacking, this method lets you combine uninsured motorist (UM) bodily injury coverage across multiple vehicles insured under the same policy.

For example, if you have two cars on the same policy and each has $15,000 in UM coverage, stacking them gives you a total of $30,000 in protection if you're hit by an uninsured driver. Vertical stacking only works if you insure more than one vehicle under the same policy, so it’s ideal for multi-car households looking to increase their coverage.

Insurance stacking isn’t available in every state. According to Allstate, 32 states allow at least one form of insurance stacking, while 18 states prohibit it. Twenty-two states allow both vertical and horizontal stacking, while 10 only allow vertical stacking.

You can review the table below to see which type of stacking is allowed in your state.

Even if your state allows stacking coverage, your insurer may not. Some states also have specific limits in place for stacking, so speak to your provider directly to explore your options for coverage.

Stacked insurance can be worth it if you own multiple vehicles or are listed on more than one policy. It increases your protection if you’re hit by an uninsured motorist by combining coverage limits, often for just a few extra dollars a month.

If you're only insuring one car, unstacked coverage might be the more practical choice. But in states with a high percentage of uninsured drivers, stacking offers added security.

We list the least and most insured states in the tables below.

The following states have the highest percentages of uninsured drivers, with Mississippi topping the list with 29.4% of drivers uninsured. Residents who want extra protection should consider stacked insurance.

These states have the lowest percentages of uninsured drivers, with New Jersey having the lowest at 3.1%. Unstacked coverage may be sufficient for many drivers in these low-risk states.

Your location and the number of vehicles you own determine which option makes the most financial sense. For multi-car households in higher-risk areas, stacking your uninsured motorist coverage could provide valuable extra protection and be worth the added premium. If you only insure one vehicle or live in a low-risk state, unstacked coverage may be the more cost-effective choice.

Stacked insurance increases uninsured motorist coverage by combining limits across vehicles or policies. It is a valuable option for multi-car owners or if you live in a state with a high number of uninsured drivers. However, it comes with slightly higher premiums. If you’re in a low-risk state or only insure one vehicle, unstacked coverage usually provides adequate protection at a lower price.

The choice between stacked and unstacked insurance depends on your location, coverage needs and budget.

Stacked insurance can help protect you in the event of an accident. We answer some frequently asked questions about insurance stacking.

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