Now more than ever, residents of large American cities face a conundrum when deciding whether to rent or buy. Renting is increasingly popular in major markets as housing prices in these desirable areas keep creeping up. Now, Zillow has announced a tool to help people determine how long they would have to own a home in their market for it to be more financially viable than renting.

The online real estate giant has unveiled its “breakeven horizon” feature that shows at what point owning makes more financial sense than renting. Zillow calculates the average up-front costs of owning a home, like a down payment, mortgage, fees and insurance premiums and determines how long one would have to stay in a home to recoup those costs.

Nationwide, it would take two years and one month before it would make sense for someone paying the national median rent to buy a house at the national median value, according to Zillow.

In more expensive cities, the “breakeven horizon” is much longer, as it would take longer to recoup the higher home costs when compared to renting in those markets. Boston has a breakeven horizon of two years and seven months, six months longer than the national average.

That’s the 12^th longest breakeven horizon in the country, Zillow reports. Boston’s time to break even on a home purchase has actually decreased marginally, the only city in the top 12 to have a decline in its breakeven horizon number. But Boston homeowners make up for it with an annual expected home value appreciation of 3 percent.