WASHINGTON — Christmas at the White House isn’t for sissies.

Take quantities that might work in a private home – guests, cookies, parties, cards, whatever – and add some extra zeros to get a feel for a White House-sized holiday season.

As in 50,000 guests, 28 parties and open houses, a couple hundred thousand holiday cards and untold quantities of cookies, cakes, brownies, truffles and the like to feed the Obamas’ holiday throng.

“They eat like crazy,” said former White House executive chef Walter Scheib, who cooked for the masses under Presidents Bill Clinton and George W. Bush.

“Christmas at the White House is the single most mentally and physically challenging thing that you can do.”

Scheib said the staff used to joke during the holidays about “White House flex time” – when “you can work any 100 hours you want this week.”

As far back as October, pastry chef Bill Yosses’ team was plotting strategy and going over drawings for this year’s gingerbread house – a 390-pound behemoth whose construction required the use of a band saw.

Yosses stockpiles mounds of cookie dough in the freezer to keep up with day-to-day demand for holiday sweets.

This year’s menu for the White House dessert buffet table includes lemon layer cake, brownies, assorted cookies, pecan pralines, pumpkin pie, chocolate truffles, and more.

Roland Mesnier, one of Yosses’ predecessors, said he always tried to sock away enough dough for 120,000 cookies and sweets by Dec. 1.

“If I did not have that, I would be in trouble,” Mesnier said.

President Barack Obama and first lady Michelle, meanwhile, might want to stockpile hand sanitizer: There’s a whole lot of handshaking going on at all those parties and receptions

– although White House aides say the Obamas are doing away with formal receiving lines and posed photos with each guest at some events to accommodate more people.

One complicating factor this season is tighter scrutiny of who’s getting in the door. Washington still is abuzz over how a couple of aspiring reality TV stars managed to talk their way into the first state dinner of the Obama White House last month. After investigating what went wrong, the White House promised to station its own staff at checkpoints to help the Secret Service determine who is cleared for entry.

And, in tight economic times, it wouldn’t do to look too extravagant. So this year’s trees feature “recycled” ornaments from presidents past that were shipped all over the country to community groups, which redecorated them with scenes of local landmarks. It was part of what staff described as an effort by the Obamas to ensure a frugal and environmentally friendly holiday season.

And each year, costs are held down by a host of volunteers clamoring to help dress up the White House. This year’s volunteers included Simon Doonan, creative director of Barneys New York. He helped design the displays.

Partners George Griffith and Mark O’Brien of the Flower Barn in Westmont have helped decorate the famous house since 1981 and contributed once again this year.

“It is a very humbling,” Griffith said. “To work in that space ... for the most powerful man, perhaps in the world – whatever president that may be.

“It overcomes everyone.”

Griffith called the task of decorating the White House for Christmas a “monumental job.”

But he said each president has been very appreciative.

“It is really something else,” Griffith said, summing up the experience.

Through the decades, White House holiday festivities generally have become more elaborate, according to Jennifer Pickens, whose new book “Christmas at the White House,” details how holiday celebrations have grown.

The pasty chef’s creation of a gingerbread house, for example, began in 1969 with a simple

A-frame built with 16 pounds of gingerbread and six pounds of icing. This year’s 56-inch-by-29-inch re-creation of the White House weighed in with 140 pounds of gingerbread coated with 250 pounds of white chocolate.