Limits

Lists information about limits in your org. This resource is available in REST API version 29.0 and later for API users with the View Setup and Configuration permission. The resource returns these limits:

Daily API calls
Daily asynchronous Apex method executions (batch Apex, future methods, queueable Apex, and scheduled Apex)
Daily Bulk API calls
Daily Streaming API events
Streaming API concurrent clients
Daily generic streaming events (if generic streaming is enabled for your org)
Daily number of mass emails that are sent to external email addresses by using Apex or Force.com APIs
Daily number of single emails that are sent to external email addresses by using Apex or Force.com APIs
Concurrent REST API requests for results of asynchronous report runs
Concurrent synchronous report runs via REST API
Hourly asynchronous report runs via REST API
Hourly synchronous report runs via REST API
Hourly dashboard refreshes via REST API
Hourly REST API requests for dashboard results
Hourly dashboard status requests via REST API
Daily workflow emails
Hourly workflow time triggers
Hourly OData callouts

The resource also returns these limits if the API user has the Manage Users permission.

Data storage (MB)
File storage (MB)

URI: /vXX.X/limits/
Formats: JSON, XML
HTTP Method: GET
Authentication: Authorization: Bearer token
Example: See List Organization Limits.

Force.com REST API Developer Guide

Limits