SAN FRANCISCO — Elon Musk said Twitter is now worth about $20 billion, according to an email he sent the company’s employees on Friday, a significant drop from the $44 billion that he paid to buy the social network in October.

The email, which was viewed by The New York Times, was sent to employees to announce a new stock compensation program. In it, Mr. Musk warned workers that Twitter remained in a precarious financial position and, at one point, had been four months away from running out of money. He said “radical changes” at the company, including mass layoffs and cost cutting, were necessary to avoid bankruptcy and streamline operations.

“Twitter is being reshaped rapidly,” Mr. Musk wrote, adding that the company could be thought of as “an inverse start-up.”

Twitter’s value has declined as Mr. Musk has dramatically overhauled the company. In October, Mr. Musk took Twitter private, which means it is no longer obligated to provide transparency about its finances. But the billionaire has indicated publicly that the company lost revenue as advertisers fled the platform after his takeover, and suggested that Twitter was in danger of bankruptcy.

The $20 billion figure values Twitter slightly higher than Snap, the parent company of Snapchat, which has recently struggled with an advertising slump and predicted its revenue would fall. Snap, which has a market capitalization of about $18 billion, has about 375 million daily active users, compared with Twitter’s 237.8 million in the company’s final public disclosure before it went private.

Mr. Musk did not respond to a request for comment and an email to Twitter’s communications department was returned with a poop emoji. The company’s new valuation was earlier reported by The Information.

According to Mr. Musk’s email about the new stock compensation program, Twitter employees will receive stock in X Corporation, the holding company he used to buy the company. Those awards will be granted under the $20 billion valuation. Mr. Musk also said in the email that he believed Twitter could someday be worth $250 billion.

Twitter will plan to allow employees to sell the stock every six months, Mr. Musk added, akin to the practice at SpaceX, his privately held rocket manufacturer. The sales of private stock would allow employees to have “liquid stock, but without the stock price chaos and lawsuit burdens of a public company,” Mr. Musk wrote.