Online retirement-planning calculators ask you a variety of financial, lifestyle and health questions, then estimate how much you might need to save, spend and invest to afford the lifestyle you want and not run out of money.

My favorite calculators…

AARP Health Care Costs Calculator estimates your health-care costs based on a database of $136 billion in actual retiree insurance health-care claims. The calculator shows how your potential costs in retirement might change depending on specific factors such as what age you retire and 82 ­specific medical conditions. Graphs show how your total health-care costs might vary year by year, plus how much Medicare is likely to cover and what you may need to pay out-of-pocket.

AARP Long Term Care Calculator allows you to compare types of care services in your area and their costs, including nursing homes, assisted-living facilities and home health aides. (click the magnifying glass, then type in “Long Term Care Calculator”)

BlackRock Retirement Expense Worksheet lets you list and track dozens of essential and discretionary expenses on an interactive PDF. (search for “Retirement Expense Worksheet”)

T. Rowe Price Retirement Income Calculator helps preretirees figure out how to meet retirement spending needs…and if you already are retired, it helps you determine whether your current level of spending is sustainable. It also helps you choose suitable investments. I like its extensive use of visually rich and easy-to-understand graphics and pie charts. www3.TRowe