When you send a snail mail package or letter, unless you pay for tracking, you may not know exactly when it will arrive. If you stick your rent check in the mail on June 27, will it reach your landlord across town before the end of the month?

There’s a handy map to tell you. While they’re not exact predictions, the United States Postal Service has what’s called “service standards,” which dictate the agency’s goals for how long it should take a piece of mail to travel from one zip code to another. The map, which depicts the USPS's service standards as of April 1, is organized by both the class of mail (First-Class Mail, Standard Mail, etc.) and by the zip code of origin.

By consulting the map, you can figure out your mail’s travel timeline and see a rough portrait of how mail travels throughout the country. It varies not just by state, but by region. For instance, a magazine (Periodicals class) originating in Portland, Oregon, should arrive in Seattle in three days, but will take four days to arrive in eastern Washington. Standard Mail might take as long as five days to reach Seattle, as seen below:

A color-coded map of USPS service standards for mail originating in Portland.
USPS

If you spring for first class mail, you can expect more speed. A piece of First-Class Mail sent from New York City will reach most locations in the northeastern U.S. in two days, and the rest of the continental U.S. in three.

A color-coded map of USPS service standards for mail originating in NYC.
USPS

If you want to reach Guam, First-Class Mail will take five days, though that’s a pretty far cry from the 17 days the same route takes via Standard Mail:

A color-coded map of USPS service standards for mail originating in NYC.
USPS

Again, all these are standards, meaning they don’t necessarily reflect the reality of every mail delivery. But they are a good way to estimate when you can expect that postcard or check to arrive once you stick it in the mail if everything goes right.