What is an API rate limit?

An API rate limit is a restriction set by an API provider on how many requests you can make within a specific time window, such as requests per second (RPS), per minute (RPM), per hour, or per day. Exceeding the limit typically results in HTTP 429 (Too Many Requests) responses.

How do I calculate my remaining rate limit buffer?

To calculate remaining buffer, track your requests within the time window and subtract from the limit. For example, if an API allows 1000 requests per hour and you've made 647, your remaining buffer is 353 requests. The calculator automates this for per-second, per-minute, per-hour, and per-day limits.

What happens when I exceed an API rate limit?

Most APIs return a 429 Too Many Requests status code when you exceed the rate limit. Many also include Retry-After headers indicating when you can try again. Strategies to avoid hitting limits include: implementing exponential backoff, batching requests, requesting higher tier limits, and pre-calculating your safe request budget with this calculator.

API Rate Limit Calculator

Check if your API usage fits within rate limits, see your remaining buffer, and estimate costs for paid APIs.

Your Usage

Requests

Per

Rate Limit

Max Requests

Per

Common API Rate Limits

Cost Calculator (Optional)

Price per 1K requests ($)

Est. Daily Volume

✅

Within Limits

You're using 20% of your rate limit

Used: 20% Buffer: 80%

Requests Used

1,000

Rate Limit

5,000

Remaining

4,000

Usage Ratio

20%

Per Second (avg)

0.28

Per Minute (avg)

16.67

Per Hour (avg)

1,000

Per Day (avg)

24,000

How Rate Limiting Works

API rate limits control how many requests you can make in a given time window.

Key Concepts

Rate limit: The maximum number of requests allowed in a specific time window (second, minute, hour, or day)
Usage: How many requests you're making in that time window
Buffer: The gap between your usage and the limit — essential for handling traffic spikes
429 Too Many Requests: HTTP status when you exceed the limit — your requests will be blocked

Frequently Asked Questions

Common questions about API rate limits and this calculator.

The API returns HTTP 429 (Too Many Requests). Your request is rejected, and you typically need to wait for the time window to reset. Some APIs include Retry-After headers telling you when to retry.

Aim for at least 30-40% buffer for production applications. This gives you room for traffic spikes, retries, and batch operations. If your buffer is below 20%, consider upgrading your plan or optimizing your requests.

Enter the price per 1,000 requests and your estimated daily volume. The calculator shows monthly cost. Most APIs charge per 1,000 requests beyond a free tier — check your provider's pricing page.

APIs choose time windows based on their infrastructure and use case. Per-second limits prevent burst abuse. Per-minute and per-hour limits balance fairness with flexibility. Per-day limits accommodate varying usage patterns.