Most of the attention in a life insurance purchase goes to the coverage amount. The term, meaning how many years the policy lasts, gets decided in a sentence, and it is the decision people most often get wrong. Too short, and the coverage ends while someone still depends on you, at an age when replacing it is expensive or impossible. Too long, and you pay a higher premium for years nobody needed protecting. Here is how to size it.

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Term life is sold in fixed lengths with a level premium for the whole period. The standard options are 10, 15, 20 and 30 years. Thirty-five- and 40-year terms exist, sold by a small number of insurers, but they are rare. Each step up in length costs more per month, because the insurer is locking in your rate through older, riskier years. Whole life, the alternative, lasts for life at a far higher premium; the trade-offs are in Term Life vs. Whole Life: Pros and Cons.

Match the term to your longest obligation

The right term is the number of years until the last person who depends on your income stops depending on it. Three obligations set that date for most households.

  • The mortgage. If a spouse would struggle to carry the house alone, the policy should last until the loan is gone. A 30-year mortgage taken this year argues for a 30-year term, or a 20-year term if you genuinely expect to pay it down early. Whether that shorter payoff is realistic is the subject of 15-Year vs. 30-Year Mortgage: Which Saves You More in 2026?
  • The youngest child. A child born today reaches adulthood in 18 years and, if you intend to see them through college, financial independence in their early twenties. Count from the youngest child, not the oldest, and round up to the next standard term: a newborn means 20 years at minimum, and 30 if you want a margin.
  • Retirement. Once your savings could replace your income for a surviving spouse, the need for insurance fades. If you are 40 and expect to retire at 65, a 25-year gap points to a 30-year term. If you are 50 with a healthy nest egg, 10 or 15 years may be plenty.

Savings shorten the answer. College accounts that are already funded remove the college years from the calculation; a retirement balance that could support your spouse removes the retirement years. Run the exercise honestly, and do it again whenever a major obligation appears or disappears.

Why “buy short and renew later” fails

The tempting shortcut is a 10-year policy now, with a plan to renew or rebuy when it ends. Three things go wrong.

First, renewal is not what people picture. When the level period ends, most policies continue as annually renewable term at attained-age rates: no new exam, but the premium jumps to several times the level premium in the first renewal years and rises again every year. It is designed as a stopgap, not a second decade of coverage.

Second, a fresh policy at an older age costs more. Term premiums rise roughly 4.5% to 9% for every year of age, so the same coverage bought at 45 instead of 35 is priced off a decade of that compounding. Third, and least predictable, your health may not cooperate. A diagnosis in the intervening years can raise the price sharply or make you uninsurable, and by then the conversion option that would have let you switch to permanent coverage without underwriting may have closed; those windows often shut years before the term ends or at a set age. The cost of waiting, in dollars, is worked through in When Is the Right Time to Buy Life Insurance?

Laddering: buy several terms instead of one

Obligations do not all end on the same day, so the coverage does not have to either. Laddering means buying two or three policies with different lengths so that total coverage steps down as needs shrink: a 30-year policy sized to the long tail, a 20-year policy for the child-rearing years, and a 10-year policy for the stretch when the mortgage balance and the daycare bills are both at their peak. Because you stop paying for each layer as it expires, a ladder typically costs less over its life than a single large 30-year policy of the same starting size. It also fails gracefully: if your finances improve faster than expected, you can let a layer lapse without touching the others.

When no term is long enough

Some needs never expire: a child with a lifelong disability, an estate that will owe taxes, or a desire to leave a guaranteed sum whenever death comes. Those call for permanent coverage, and the usual structure is a large term policy for the years of maximum obligation plus a small whole life policy that outlasts it. Buy the permanent piece young if you buy it at all; the premium is set by your age and health at purchase and never goes down.

A quick decision rule

  • List the year each obligation ends: mortgage payoff, youngest child’s independence, retirement.
  • Take the latest of those dates, count the years, and round up to the next standard term.
  • If the layers are very different in size or timing, split the coverage into a ladder.
  • Buy a convertible policy and note the conversion deadline, so the option to go permanent later stays open.