Worried about outliving your retirement savings?

One of the biggest challenges of retirement is making sure your money will last the rest of your life—however long that might be. You can only estimate how many years you will live, and you have to manage your finances so your savings will last for that unknown number of years. Here are some ways to make sure you will have money coming in, no matter how long you live:

Social Security. Social Security is your first line of defense against outliving your savings because these payments will continue for the rest of your life and are adjusted for inflation each year. Anyone who qualifies for Social Security will never completely run out of money, but could have to cut their standard of living to survive on their Social Security payment if they exhaust all other sources of income. Since this is the only guaranteed source of income most retirees have, it's a good idea to try to increase the amount you will get. Common strategies for boosting your Social Security payments include making sure you have at least 35 years of covered earnings, claiming spousal payments, and delaying claiming up until age 70

A pension. Workers fortunate enough to get a traditional pension through their jobs generally have a second guaranteed source of monthly retirement income. Most private-sector pension plans are insured by the PBGC, which guarantees pension benefits up to certain annual limits and will pay out benefits if your former employer goes out of business.

An annuity. Immediate annuities allow you to hand over a chunk of your retirement savings to an insurance company in exchange for guaranteed monthly payments for the rest of your life.  You gain a predictable monthly income, even if you live past age 100 or the stock market takes another dive. "With the insurance company annuity, the insurance company guarantees that the money will last the rest of your life no matter how long you live," says Steve Vernon, a fellow of the Society of Actuaries and author of "Money for Life: Turn Your IRA and 401(k) into a Lifetime Retirement Paycheck.  With the various different types of annuities, it is a good idea to work with an independent agency that will have access to multiple companies products.

Pay off your house. Paying off your mortgage eliminates one of your biggest monthly bills and allows you to use your savings for other expenses besides housing. The equity in your home could also be tapped for extreme emergencies, via a second mortgage or reverse mortgage. "If you pay off your house, that's a guaranteed return of 3 to 4 percent," says Stephen Curley, a certified financial planner and director at Water Oak Advisors.  "If you go into retirement debt-free and owning your house outright and you are able to take out 4 percent of your portfolio along with Social Security and meet your retirement needs, that is the best-case scenario. And if you can't stand the capital market, you should buy a fixed immediate annuity."