President Donald Trump's personal helicopter is seen at the Mar-a-Lago estate in Palm Beach, Florida, Apr. 9, 2017. Reuters

President Donald Trump is fast approaching his hundredth day in office – many of which have been spent far from the White House. By the end of his 13th week as president, Trump spent 25 days at Mar-a-Lago, his estate in South Florida.

Past presidents spent significantly less time away from Washington, D.C., during the same period. Former President Barack Obama spent four days away from the White House, while his predecessor George W. Bush spent 14 days away. Bill Clinton, for his part, did not spend any days away in his first 13 weeks.

Read: President Trump Spends $10 Million On Travel In First Four Weeks

Trump’s frequent travel comes with a hefty price tag. It’s difficult to pin down exactly how much the president’s travel costs and estimates on the subject differ. Trump often invites foreign leaders to the estate, further complicating the cost calculations. The website IsTrumpAtMaraLago.org, launched by the Center for American Progress Action Fund, purports to be tracking the expenses of Trump’s Florida trips, pinning them at about $25 million in the first 13 weeks.

The website cites a figure from a Government Accountable Office report which states that each trip to Mar-a-Lago costs taxpayers $3.6 million. However, that figure actually comes from a report which has nothing to do with Trump—instead, it’s from an October 2016 GAO report regarding Obama’s travels. The specific figure looked at one of Obama’s first trips to Palm Beach, though it included part of a trip to Chicago where Obama gave a speech before flying to Florida. Lower estimates put a price tag of about $1 million on each Mar-a-Lago trip, according to the Associated Press.

Though the exact cost of the trips remains unknown, it’s clear that Trump will quickly outpace his predecessor’s travel expenditures. Obama spent slightly under $97 million on travel in his eight years as president, according to conservative government watchdog Judicial Watch. Judicial Watch said they were in the process of calculating Trump’s travel expenses.

The Trump administration defended the president's frequent travel after it came under fire.

"He is not vacationing when he goes to Mar-a-Lago," White House spokeswoman Stephanie Grisham told the Washington Post in February. "The president works nonstop every day of the week, no matter where he is."

President Donald Trump and Chinese President Xi Jinping walk along the front patio of Mar-a-Lago after a meeting in Palm Beach, Florida, Apr. 7, 2017. Reuters