For calendar, here is the documentation to know the usage limits.
The Google Calendar API has a courtesy limit of 1,000,000 queries per
day.
To view or change usage limits for your project, or to request an
increase to your quota, open the API Library in the Developers
Console.
If you have enabled billing for your project, you can see the
quota percentage for each API. You can view and change quotas from the
API section's API Library and Enabled APIs links. Selecting an
API from the API Library list or from the Enabled APIs page takes you
to a page with overview, usage, and quota links for that API. Choosing
Quotas lets you view and change quota-related settings. Choosing Usage
provides you with usage statistics as well as response code and method
information.
And for maps, you can visit this documentation.
Standard Usage Limits
Users of the standard API:
- Free until exceeding 25,000 map loads per 24 hours
Note: Quota exceptions may apply. Learn more here.
Enable pay-as-you-go billing to unlock higher quotas:
After exceeding the free usage limits, billing at $0.50 USD / 1000
additional requests, up to 100,000 per 24 hours.