Here's the share of income that goes to rent in cities across the country

When you browse rental listings in different spots across the country, you can come across both eye-popping high prices and equally surprising low ones. Whether any of them are actually affordable for you is another question.

One way to measure rent affordability is to consider not just the price itself, but the share of your income that it devours. The above map shows how much of a city's average income goes toward rent for a one-bedroom apartment, using 2018 data from both real estate site Zillow and the U.S. Bureau of Labor Statistics.

"The general rule of thumb is that 30 percent is a comfortable range," said Lawrence Yun, chief economist for the National Association of Realtors.

More from Personal Finance:
Employers are hiring, but don't expect a bigger paycheck
Your $50,000 annual income goes further in these cities
Retiring past age 65? Avoid costly Medicare mistakes

There can be a big disparity in that recommended share when you compare similar rent prices in different cities.

For example, the median rent — half fall below, half above — of $1,405 in Hilton Head, South Carolina, is 42 percent of the area's $39,700 average annual salary. In Boulder, Colorado, a similar median rent of $1,450 eats up a smaller share — 28 percent — of the city's average income of $62,650.

Of course, even if you can stay within that 30 percent recommendation, whether it's realistic depends on your other financial obligations. And, state and local taxes also make a difference in how much cash you'll end up with in your paycheck.

Rent tends to be more of a budget-buster in coastal cities. For example, in Los Angeles, the median rent of $2,095 is 45 percent of the $55,820 average salary. In New York , median rent of $2,100 is 40 percent of the metro area's average $62,870 income.

"The affordability gap has been widening," Yun said. "Ten or 20 years ago, cities like New York City and San Francisco were expensive relative to middle America, but now that gap is bigger.

"Unless people earn top dollar it can be hard to afford rent in those cities."

While there are some Midwestern spots that surpass or get close to the 30 percent affordability measure, the region generally tends to have more affordable housing.

For instance, in Bloomington, Illinois, the $593 median rent only eats up 13 percent of the city's average $53,140 salary. In Cedar Rapids, Iowa, median rent of $515 is also 13 percent of the city's average salary of $48,410.

"I'd say consider Middle America as a place to establish a career," Yun said. "Even if you get a lower wage than somewhere else, it could come with more purchasing power."