[Serie: All About Japanese Particles]
1. Indicates an approximate amount or extent; in contrast with hodo and bakari, kurai denotes an approximate quantity without connoting its upper or lower limits: “approximately, about.”
Note: Hodo (#20, no. 1) and bakari (#21, no. 1) may replace kurai in this usage.
ここからその学校まで車30分ぐらいかかります。
Koko kara sono gakkō made kuruma de sanjuppun gurai kakarimasu.
It takes about thirty minutes by car to get to the school from here.
昨日のパーティーに来た人は、100人ぐらいだったと思います。
Kinō no pātī ni kita hito wa, hyakunin gurai datta to omoimasu.
I think about 100 people came to the party yesterday.
2. Indicates the extent of an action or condition after a specific example is given: “so … that, to the extent that.”
Note: Hodo (#20, no. 3) may replace kurai/gurai in this usage.
安田さんの旅行の話は面白くて、時間のたつのも忘れたくらいだった。
Yasuda-san no ryokō no hanashi wa omoshirokute, jikan no tatsu no mo wasureta kurai datta.
Yasuda’s stories of her trip were so interesting that we lost track of time.
恥ずかしくて穴があったら入りたいぐらいだった。
Hazukashikute ana ga attara hairitai gurai datta.
I was so embarrassed that I felt like crawling in a hole. (Lit., … if there had been a hole, I would have wanted to go in it.)
3. Indicates a comparison: “as … as.”
Note: Hodo (#20, no. 2) may replace kurai/gurai in this usage.
山下さんの新しい家の庭は、ゴルフ場ぐらいの大きさだ。
Yamashita-san no atarashii ie no niwa wa, gorufu-jō gurai no ōkisa da.
The garden at Yamashita’s new house is as big as a golf course.
自分の家くらい、いい場所はない。
Jibun no ie kurai, ii basho wa nai.
There’s no place as nice as one’s own home.
– Source: All about particles – A handbook of Japanese function words –