衛生紙用完了，我必須去買。

We're out of tissue paper, so I need to go buy some.

We're out of tissue paper, so I've got to go buy some.

Source: Tatoeba

Sentence Composition

1 衛生紙 wèishēngzhǐ
  1. toilet paper
  2. bathroom tissue
2 用完 yòngwán
  1. used up
  2. finished
=3 了 le
  1. (completed action marker)
  2. (modal particle indicating change of state, situation now)
  3. (modal particle intensifying preceding clause)
=3 了 liǎo
  1. to finish
  2. (used with 得 dé or 不 bù after a verb to express (im)possibility, as in 忘不了 wàngbuliǎo "cannot forget")
  3. (literary) (usually followed by a negative such as 无 wú or 不 bù) completely (not); entirely (not); (not) in the least
  4. to understand clearly (variant of 了 liǎo)
=3 了 liǎo
  1. (of eyes) bright
  2. clear-sighted
  3. to understand clearly
=3 了 liào unofficial variant of 瞭 liào
4 我 wǒ
  1. I
  2. me
  3. my
5 必須 bìxū
  1. to have to
  2. must
  3. compulsory
  4. necessarily
6 去 qù
  1. to go
  2. to go to (a place)
  3. (of a time etc) last
  4. just passed
  5. to send
  6. to remove
  7. to get rid of
  8. to reduce
  9. to be apart from in space or time
  10. to die (euphemism)
  11. to play (a part)
  12. (when used either before or after a verb) to go in order to do sth
  13. (after a verb of motion indicates movement away from the speaker)
  14. (used after certain verbs to indicate detachment or separation)
7 買 mǎi
  1. to buy
  2. to purchase