Well, they had no excuse not to call home for the holidays.

City jailbirds made an average of 32,487 outgoing calls every day since they were gifted free phone privileges in May — a nearly 30-percent boost from their prior activity, The Post has learned.

The hundreds of thousands of calls lasted an average of 7.58 minutes — more than one-third of the 21 minutes of phone time inmates are now allotted every three hours on the taxpayer’s dime, according to data from the city’s Department of Correction spanning May 1–Dec. 1.

The gabfest, which began in May under a law spearheaded by City Council Speaker Corey Johnson (D-Manhattan) may be toll-free for inmates, but it’s been projected to cost $8 million in public funds every year.

“We need to treat inmates as humans who deserve to communicate with family and friends, not as people to exploit,” said Johnson. “Maintaining community contact is correlated with a reduction in recidivism that should actually keep New York safer.”

The cost includes $5 million in now-lost revenue the city was previously pocketing when the calls cost chatty inmates — 50 cents for the first minute, a nickel for each additional minute — and $3 million the city now shells out to telecom company Securus, to cover their own lost share.

As of Dec. 1, convicts and pre-trial detainees had so far racked up a cumulative phone bill of more than $1.6 million, according to the DOC.

Despite the hefty sum, authorities defended the expanded access to phones as integral to easing inmates eventual reintegration to society.

“The fact is when individuals remain in contact with their community while incarcerated, the likelihood of rehabilitation is much greater,” said DOC spokesman Peter Thorne.

But the phone free-for-all is getting a different reception from those tasked with keeping the peace on the inside — and monitoring all those calls.

“With the uptick in calls is obviously an increase in work for our Gang Intelligence Unit, who work diligently to ensure no criminal activity is taking place on these calls,” said Elia Husamudeen, president of the Correction Officers’ Benevolent Association.

Added Joseph Russo, president of the Assistant Deputy Wardens / Deputy Wardens Association, “I think it should be a crime to force New York City taxpayers, including crime victims, to fund $8 million a year for jail inmates to make 32,000 calls a day.

“This is another outrageous concession to New York City criminals.”