Calculate API throttling parameters: request quotas, QPS, concurrency, window size
Zero Dependencies · Works Offline📝 Rate Limit Configuration
📄 Algorithm Analysis
What Can the API Rate Limit Calculator Do?
The API Rate Limit Calculator is a free online developer tool that helps design and compute API throttling strategy parameters. It supports four mainstream rate limiting algorithms: token bucket, leaky bucket, fixed window, and sliding window, calculating key metrics like QPS, RPM, max concurrency, and utilization. Ideal for API gateway configuration, microservice throttling design, and capacity planning. All calculations are performed locally in the browser—your data is never uploaded to any server.
Core Features
- Multi-Algorithm Support: Token bucket, leaky bucket, fixed window, and sliding window parameter calculation
- Key Metrics: QPS, RPM, max concurrency, utilization and other core indicators
- Burst Analysis: Token bucket burst traffic handling capacity calculation
- Concurrency Estimation: Estimate max concurrent connections based on request latency and QPS
- Configuration Suggestions: Rate limit configuration recommendations based on algorithm characteristics
Usage Tutorial
1. Select the rate limiting algorithm type (token bucket/leaky bucket/fixed window/sliding window).
2. Enter the request quota and time window size.
3. Set burst capacity, request latency, and concurrency parameters.
4. View calculation results and configuration suggestions for each algorithm.
Application Scenarios
Scenario 1: API Gateway Configuration
Backend developers configuring Kong/Nginx/API Gateway need to calculate appropriate rate limit parameters to prevent service overload.
Scenario 2: Microservice Throttling Design
Architects designing microservice rate limiting strategies calculate throttling thresholds for each algorithm based on service capacity.
Scenario 3: Capacity Planning
Operations teams calculate rate limit parameters and resource quotas that need adjustment based on business growth projections.
Extended Knowledge
API rate limiting is a core protection mechanism in distributed systems. The token bucket algorithm generates tokens at a fixed rate, allowing burst traffic (tokens can be consumed quickly when available), suitable for most API scenarios. The leaky bucket algorithm processes requests at a fixed rate, smoothing output traffic, suitable for scenarios requiring strict rate control. The fixed window algorithm counts within a fixed time window—simple to implement but has boundary burst issues. The sliding window algorithm subdivides the window into multiple sub-windows, solving boundary burst problems with higher precision. Little's Law is the basis for concurrency calculation: Concurrency = QPS × Average Latency.
❓ FAQ
What is API rate limiting?
API rate limiting controls the number of requests a client can make within a specified time window, preventing service overload and abuse.
Token bucket vs leaky bucket?
Token bucket allows burst traffic; leaky bucket processes at a fixed rate. Token bucket is better for scenarios allowing short bursts.
How to calculate QPS?
QPS = Total requests / Time window (seconds). E.g., 1000 requests / 60 seconds ≈ 16.67 QPS.
Is data uploaded to a server?
No. All calculations are performed locally in your browser.
Which algorithms are supported?
Token bucket, leaky bucket, fixed window counter, and sliding window log.
How to determine appropriate parameters?
Based on service capacity, user scale, and business tolerance. Generally set limits to 70-80% of capacity.