API Rate Limit Calculator

Calculate optimal rate limit settings from expected traffic, peak multipliers, and SLA requirements.

Average requests/sec

Peak traffic multiplier

Burst window (seconds)

Safety margin %

Max concurrent users

Avg requests per user/min

Tab to move between fields

Peak RPS

300

Rate limit / window

21,600

Per-user limit / window108

Throttle threshold (RPS)360

Daily requests (avg)8,640,000

Daily requests (peak)25,920,000

Est. throttled % at 1.5x peak20

How to Use This Calculator

Enter your Average Requests per Second and Peak Traffic Multiplier (e.g., 3x for traffic spikes).
Set the Burst Window (seconds) and Safety Margin % to add headroom.
Enter Max Concurrent Users and Average Requests per User per Minute.
Review Peak RPS, Rate Limit per Window, and Per-User Rate Limit.
Use the Throttle Threshold RPS to configure your API gateway or load balancer limits.

How the result changes with Average requests/sec

Average requests/sec: Average sustained requests per second during normal traffic.
Peak traffic multiplier: How many times average traffic your peaks reach (e.g., 3x = flash sale).
Burst window (seconds): Time window for rate limit counting (token bucket refill period).
Safety margin %: Extra headroom above peak to avoid false throttling.
Max concurrent users: Expected maximum simultaneous users hitting the API.
Avg requests per user/min: Typical number of API calls a single user makes per minute.

Peak RPS: Expected peak requests per second.
Rate limit / window: Maximum requests allowed in each burst window.
Per-user limit / window: Fair-share rate limit per individual user in each window.
Throttle threshold (RPS): Requests per second at which 429 responses begin.
Daily requests (avg): Total requests per day at average load.
Daily requests (peak): Total requests per day if peak load were sustained all day.
Est. throttled % at 1.5x peak: Percentage of requests that would be rejected at 150% of peak traffic.

Identify Input Parameters
4 parameters
Average requests/sec = 100, Peak traffic multiplier = 3, Burst window (seconds) = 60, Safety margin % = 20 = 6 input(s) provided
Calculate Peak RPS
Peak RPS = avgRps * peakMultiplier
300 = 300
Calculate Rate limit / window
Rate limit / window = ceil(peakRps * burstWindowSec * (1 + safetyMarginPct / 100))
21600 = 21600
Calculate Per-user limit / window
Per-user limit / window = max(1
108 = 108
Calculate Throttle threshold
Throttle threshold = round(rateLimitPerWindow / burstWindowSec)
360 = 360