It is double the size of my room.

有我房间的两倍大。

youdao

This past year at school, I lived in a standard freshman double. The room was about the size of the place where my whole family of three plus my grandmother used to live.

在过去的一学年里，我住的是专门为新生准备的标准双人间，这间屋子足有过去我们一家三口外加我奶奶住的那间屋子大小。

youdao

Your room is double the size of my room.

你的房间有我的两倍大。 double作主语补语。

youdao

The spacious double king deluxe room features a king-size bed, 42-inch flat-screen TV and a private bath with shower.

BBC: Daily deal: A night in Seattle

He meant in their own suite and in the permanent 42nd-floor residence of the U.S. ambassador to the United Nations. (I didn't get to see it because the current ambassador, Susan Rice, is living there now.) Mr. Blauvelt estimated that it is double to triple the size of the Presidential Suite, with a very large dining room.

WSJ: In the City's Power Suite