「It is the same degree as ~ / to the same extent as ~.」 Used to express the strength of a degree by comparing it to a certain situation. It is also often used in forms like 「~かと思うくらい」 or 「~かと思うほど」, as in ⑥.
例:
1. この店のパンはおいしい。毎日食べたいくらいだ。
The bread at this shop is so good; I could eat it every day.
2. よう子さんの腕は折れそうなくらい細い。Yoko's arms are so thin they look like they might break.
3. 天気予報によると、今日は台風ぐらいの風が吹くそうだ。According to the weather forecast, winds as strong as a typhoon will blow today.
4. 傘をさすほどではないが、少し雨が降っている。It's not heavy enough to need an umbrella, but there's a light rain.
5. 突然立っていられないほどの痛みを背中に感じた。I suddenly felt a pain in my back so intense that I couldn't stand up.
6. さっき地震があった。本棚が倒れるかと思うほど激しく揺れた。There was an earthquake a little while ago. It shook so violently I thought the bookshelf might fall over.