Exponential Backoff Calculator

About this tool

The uncapped wait is base times multiplier to the power of the attempt number, then cut at the cap. With "Equals the base delay", the attempt starts at 0, and multiplier to the power 0 is 1, so the first wait is the base delay. The sample is a base of 1000 ms, a multiplier of 2, a cap of 30000 ms, and 4 attempts: 1000, 2000, 4000, then 8000 ms.

"Equals base times the multiplier" starts the attempt at 1. The first wait is base times the multiplier. That is the AWS Architecture Blog simulator: pow(2, n) * base, and n is incremented before the first sleep, so the first n is 1. The simulator hardcodes 2. This page uses the multiplier you type. The source is Marc Brooker's "Exponential Backoff And Jitter" (4 March 2015) and backoff_simulator.py in aws-samples/aws-arch-backoff-simulator.

Full jitter draws a wait from 0 up to that capped exponential, using a half-open range. Equal jitter keeps half of it and draws the other half at random. Decorrelated jitter draws between the base delay and three times the previous wait, then applies the cap. The previous wait starts as the base delay. The multiplier does not enter that formula. The draws use mulberry32 and the seed, so the same seed repeats on this page. They are not Python's random.uniform, and they are not the retry schedule of a particular SDK. Each jittered wait is rounded to 0.001 ms, and the cumulative column adds those rounded waits. Up to 15 attempts.