This is a guest post written by Elizabeth Renter, from NerdWallet.

Employer-based life insurance isn’t like birthday cash from your grandmother — it’s in your best interest to question whether you’re getting enough.

Ninety-eight percent of Americans sign up when offered life insurance through work, according to the U.S. Bureau of Labor Statistics. And why not? Even if your employer isn’t footing the entire bill, group life insurance is a good buy — it’s usually cheaper than buying an individual policy and it comes without a medical examination.

But relying on this perk alone to care for your family if you die could leave them in a bind. A new report from LIMRA, an industry group, shows that 9 million households in the U.S. have only group life insurance, and these households need an additional $225,000 in coverage, on average.

How Much Life Insurance Do You Need?

Your employer may offer you life insurance that’s equal to one or two times your salary, although the amount varies by employer. If you’re single with no dependents and no significant debts, such as a mortgage, this could be enough. But for many folks, it’s not.

You generally need enough life insurance to cover your missing income for a certain number of years, to pay off your debts and to possibly pay for your children’s college education. Add these up and compare them with your group life coverage — chances are that you’re lacking.

Let’s say you make $55,000 a year and you want to ensure your family receives enough money to replace your salary for 10 years. That’s $550,000. Plus, you owe $150,000 on your mortgage and have two children whom you’d like to send to college. That could be roughly another $260,000, assuming no financial aid. Add to that any funeral expenses, and you’re looking at close to $1 million. The average household with life insurance has just $300,000 in coverage, according to LIMRA. Here are ways to determine how much life insurance you need.

Options for Additional Coverage

If you need more insurance than the basic amount you can get through work, you generally have two options: supplemental group life through work or an individual policy. You’ll want to compare life insurance rates for several policies and weigh the advantages and drawbacks of each type.

Supplemental group life insurance is offered by employers as a way for you to tack on more coverage than the standard offering. There are some upsides to this route: It’s less expensive than purchasing an individual policy and you likely won’t need a medical exam. But you may have to fill out a “certificate of insurability” or medical questionnaire. If your answers raise any red flags about your health, the insurer might ask for additional medical records or order a life insurance medical exam before approving the coverage.

Individual policies have one big advantage over group coverage: They’re portable; you don’t have to leave them behind if you change jobs. In some cases, you can convert group life insurance to an individual policy, but you’ll see a significant price increase if you do.

Life insurance through work is a valuable benefit, but don’t assume it’s enough. Evaluate your coverage needs carefully and find a solution that’s appropriate for your household’s long-term needs.

Elizabeth Renter is a staff writer at NerdWallet, a personal finance website. Email: elizabeth@nerdwallet.com. Twitter: @ElizabethRenter.