It depends on which Google service you’re using. As of right now, it varies between 20,000 to 100,000 calls per day.
Quotas for Google Services are clearly specified.
- Consumer
(e.g., gmail.com) = 20,000 / day - G Suite free edition (legacy) = 50,000 / day
- G Suite Basic / Gov & G Suite Business / Enterprise / Education = 100,000 / day