A heat map of Boston apartments by price per bedroom with MBTA route overlay.

A new tool developed by Jeff Kaufman, a 27-year-old programmer at Google in Cambridge, allows apartment renters to visualize where Boston’s most and least expensive apartments are. Kaufman's heat map displays the cost per bedroom relative to each Boston neighborhood.

The map indicates the most expensive apartments in Boston tend to hover between Back Bay and Downtown Boston and on into the Seaport District. The region’s least expensive apartments are found near Mattapan, Dorchester and Revere.

Areas of Cambridge along the Red Line also display expensive apartment listings, where the booming tech economy is squeezing commercial rents for startups.

Kaufman's first iteration of the heat map originated in 2011 when he was looking for a place to live.

"I was looking for an apartment and didn't have a good sense of how expensive different parts of the city were," Kaufman says. "I wanted to have a map that gave you a rough idea of the city and how expensive they were."

Reddit user “yiseowl” helped explain the heat map by overlaying the MBTA train map over Kaufman’s. The juxtaposition shows some correlation between rent and MBTA accessibility.

According to Kaufman’s data, which he took from apartment rental search engine Padmapper, the average cost per bedroom in 2013 is $1,314. In 2011, the average cost per bedroom was $1,141.

This is a much greater increase than inflation. The [Consumer Price Index] in June 2011 was 225.922 while the December 2012 one was 229.594, so you would expect $767/room then to turn into $780/room now instead of the $895 we actually see.

Curbed Boston also published a real-estate map in December of the 15 most expensive home sales of 2012.