JusticeFinder Tool

UM/UIM Coverage Gap Analyzer

When the driver who hit you has no insurance or not enough to cover your injuries, your own uninsured/underinsured motorist (UM/UIM) coverage is what stands between you and an unpaid balance. This analyzer compares your damages to the at-fault driver's limits and your UM/UIM coverage so you can see what's covered and what's still exposed.

Start Tool Open Spreadsheet Download Template

Find your coverage gap

Enter your damages, the at-fault driver's coverage, and your own UM/UIM limit. The layered coverage bar updates live.

Your estimated damagesTotal medical bills, lost wages, and other losses you're claiming.

At-fault driver's insuranceWhat coverage the driver who hit you is likely to have.

At-fault driver's liability limitTheir bodily-injury coverage per person. Use the Min-Insurance lookup if you're unsure of the state minimum.

Your UM/UIM limitYour own uninsured/underinsured motorist coverage per person.

StackingSome states let you stack UM/UIM across multiple insured vehicles.

Potential uncovered exposure

$100,000

$50,000 of $150,000 damages covered.

How your damages are covered

At-fault liability pays$30,000

Your UM/UIM pays$20,000

Gap — potentially exposed$100,000

This models the common UIM offset rule, where your underinsured coverage tops up only the amount above the at-fault driver's limit. Some states instead add UIM on top, and stacking rules vary — confirm your state's approach. Calculations run in your browser; nothing is saved.

Read JusticeFinder elsewhere

Short legal explainers on TikTok, visual case briefs on Instagram, daily threads on Threads — same independent editorial.

JusticeFinder Guides

Recommended Guides for Claim Strategy

Pair this calculator with the free adjuster tactics playbook and the paid claim kit to keep documentation, valuation, and negotiation aligned.

Visit Legal Guides →

Car AccidentPremiumCar Accident Master Claim KitComplete 10-step documentation system for the first 30 days after a crash.$37View guide →

Insurance DefenseFreeInsurance Adjuster Tactics Expose + Defense PlaybookFree lead magnet exposing the 12 tactics insurers use to reduce or deny claims.FreeView guide →

Why the gap matters

State-minimum liability limits are often far below the cost of a serious injury.

If your damages run to six figures and the driver who hit you carries a state-minimum policy — or no insurance at all — the liability coverage can be exhausted long before your bills are paid. Your own UM/UIM coverage is designed to fill that gap, which is exactly why it's worth understanding before you need it.

The analyzer shows the three layers stacked against your damages: what the at-fault driver's policy pays, what your UM/UIM adds, and what — if anything — remains exposed.

Offset versus add-on — a state-by-state difference

The same policy can be worth more or less depending on how your state treats UIM.

Under the common offset approach, your UIM pays only the portion of your coverage above the at-fault driver's limit. Under an add-on approach, your UIM sits on top of their liability coverage, which can produce a meaningfully larger recovery from the same limits.

This tool models the offset rule because it's the more common and more conservative of the two. Confirm your state's treatment — and any stacking rights — before you rely on the result.

Related Resources

Use these pages and documentation tools to validate the estimate, preserve evidence, and keep the claim file organized.

Related Tool

Minimum Insurance by State

Estimate the at-fault driver's likely liability limit from your state's minimum requirements.

Related Tool

Net Settlement Calculator

Once you know the coverage available, model what a settlement nets after fees and liens.

Guides

Insurance Claims Guides

Read the long-form guides on UM/UIM, stacking, and recovering from an underinsured driver.

Spreadsheet

Insurance Claim Tracker

Track each policy, limit, and adjuster as you pursue both the at-fault and UM/UIM claims.

Frequently Asked Questions

What's the difference between UM and UIM?

Uninsured motorist (UM) coverage applies when the at-fault driver has no insurance. Underinsured motorist (UIM) coverage applies when they have some insurance, but not enough to cover your damages.

What is the UIM offset rule?

In many states, UIM only pays the amount above the at-fault driver's liability limit — so a $50,000 UIM policy against a $30,000 at-fault limit effectively adds $20,000. Some states instead add UIM on top of the liability coverage. This tool models the common offset approach.

What is stacking?

Stacking lets you combine UM/UIM limits across multiple vehicles on your policy (or multiple policies), increasing the coverage available. Whether and how you can stack depends on your state and policy.

How do I find the at-fault driver's coverage?

Their limits come out in the claim. Until then, you can estimate using your state's minimum liability requirement — the Minimum Insurance by State tool shows those figures.

Educational Use Disclaimer

This analyzer is an educational coverage model only and does not constitute legal or insurance advice. UM/UIM offset versus add-on treatment, stacking rules, and policy terms vary significantly by state and carrier. Confirm how your coverage applies with your policy, insurer, or a licensed attorney before relying on any figure.

Explore More JusticeFinder Tools

Each calculator handles a different part of the claim lifecycle, from liability and deadline planning to damages and net recovery.

Damages EstimatePain & Suffering

Pain and Suffering Calculator

Estimate non-economic damages with multiplier and per diem models.