How to use this backoff calculator
Enter the first wait, the multiplier, the cap on a single wait and the retry count, and the per-attempt delay and cumulative wait appear as a table. Enter a total budget and the tool counts backwards to show how many attempts fit, and the delays are also shown as an array you can paste into code.
How the delays are derived
Each delay is min(cap, base x multiplier^(attempt-1)). With a 100 ms base, a multiplier of 2 and a 10,000 ms cap over seven attempts, the waits are 100, 200, 400, 800, 1,600, 3,200 and 6,400 ms for a total of 12,700 ms. Capping this way matches the form used in the AWS Architecture Blog article on backoff and jitter.
Limits and cautions
Only wait time is summed, so subtract request duration from the budget yourself. Randomised spread belongs to the jitter calculator and success rate estimation to the webhook retry policy tool, so neither is covered here.
Frequently asked questions
With only a multiplier, the tenth attempt waits tens of seconds. A cap keeps later attempts at a steady interval so the wait does not grow without bound.
The delays are added from the first attempt and counting stops at the attempt that would pass the budget. Only wait time is summed, so subtract request duration separately.
No. This tool covers the delay table and the budget inversion only. For a final success rate from a failure rate, use the webhook retry policy tool.