Twice as, three times as: gấp đôi, gấp ba

Gấp means "times" when you multiply an amount: gấp đôi is twice as much, gấp ba three times, gấp mười ten times. For twice, the everyday form is gấp đôi, with đôi (a pair); gấp hai lần also turns up, mostly in figures and reports. From three up, use the plain number.

Put it after the adjective, then what you compare with: Nhà này lớn gấp đôi nhà cũ. This house is twice as big as the old one. When the comparison is clear, leave it out: Ở đây tiền nhà mắc gấp ba. Rent here is three times as much. Lần (times) can follow the number, especially in writing and with bigger numbers: gấp mười lần.

It can also follow a noun, as an amount: Lương anh ấy gấp đôi lương em. His salary is double mine. After tăng (go up), it means "double" or "triple": Năm nay khách tăng gấp đôi. This year we've had twice as many customers.

For "half as much", Vietnamese uses một nửa (half) instead: Giá ở đây chỉ bằng một nửa. Prices here are only half as much.