As a small task at work, I've implemented a very simple online exponential backoff calculator.

http://backoffcalculator.com/

This can be useful, for example, if you are composing AWS Step Functions: it can give you an overview of your retry strategy, or help you tailor one.

It should be mobile friendly and totally client-side (it runs 100% in your browser).

Be sure to let me know if you find it useful, also if you experience any bugs 😊