Google Translate API Requests Limit

It seems to be 100,000.

Though this can be increased. (Refer discussion in the link)

With the (paid) google translate API v2, one can set different quotas, like a Per-User Limit, which throttles the maximum number of characters a user can send for translation / second. You can set this as low as you want, i.e. 10.0 characters/second/user.

Remark There is no more free google translate API: V1 was shut down on Dec. 1, 2011, and for V2 you have to pay. See: Google language APIs