Hundreds of thousands of people are expected to clog Washington DC for Donald Trump’s inauguration and a major demonstration the day after, but how many will actually arrive to party or protest is an open question.

Officials estimate that 800,000 to 900,000 people will be present on Friday for the inauguration, a celebration that takes over the city, closing roads and taxing the city’s Metro transit system.

Trump himself has promised “massive crowds” but just what that will mean is unclear.

Hundreds of thousands of others are expected Saturday for the Women’s March on Washington.

Women's March on Washington could outdraw Trump's inauguration https://t.co/clL3sUXfts

— COFFEE WITH NICOA (@nicoadunne) January 16, 2017

Trump showed he could draw crowds during the campaign, but his supporters weren’t so quick to make plans to be in Washington for his inauguration.

Elliott Ferguson, the president of Destination DC, the city’s convention and tourism bureau, said that before Election Day hotels had more events tentatively planned for a Hillary Clinton victory than a Donald Trump one.

And when Trump won, the “level of enthusiasm” and demand for hotel rooms did not immediately reach that of past recent inaugurations, he said.

“No one’s phones were ringing” on the day after the election, he said.

Things started to pick up after New Year’s but some hotels have cut back minimum-night stays from four nights to two.

Women’s March on DC Will be Big, and It Might be Uncomfortable. That’s How It Should Be. https://t.co/SiuCZ860uf – @Sierra_Magazine

— Liz Williams (@lizzwill) January 16, 2017

Some hotels are only 50 per cent full, though higher-end hotels apparently have more bookings.

“It’s been much, much slower than anyone would have anticipated for a first-term president,” he said.

Saturday’s march has helped drive more reservations, he said.

“The moment it was confirmed it was happening in the city our hotels were seeing reservations take place.”

"The largest mass mobilization that any new administration has seen on its first day.” @lsarsour 💜 https://t.co/xR2r4vk0C0

— Rama Issa-Ibrahim (@ramitcha1) January 11, 2017

City planners are betting that Trump’s inauguration is more like President Barack Obama’s second inauguration in 2013, which drew more than 800,000, rather than Obama’s first in 2009, which drew 1.8 million people.

But while officials have experience and historical data to draw on to estimate crowds for Friday, guessing how many people will show up for Saturday’s demonstration is harder.

Women’s March on Washington organisers said in applying for a demonstration permit that they expected 200,000 people.

Cher is among the Hollywood stars planning to march in Washington on inauguration day. Photo: AP/Carolyn Kaster

Christopher Geldart, the District of Columbia’s homeland security director, thinks the march will draw more than that.

Some 1,800 buses have registered to park in the city on January 21, which would mean nearly 100,000 people coming in just by bus, Geldart said.

Amtrak trains into and out of the city are also fully booked on that day, Geldart said.

“Usually when I look at things like that, that tells me we’ve got a pretty substantial crowd coming in,” he said.

“That leads me to believe we’re definitely above the 200,000-person mark.”

Hollywood notables plan to turn out in force for the march, including Cher, America Ferrera, Katy Perry, Amy Schumer, Scarlett Johansson, Julianne Moore and Frances McDormand.