timelapse CALC will help you determine the final length of your time-lapse clip.
Based on the shutter interval, shooting duration and desired framed rate it will indicate the result on a hh:mm:ss format display along with the total frame number.
One main purpose of this utility is to keep it simple and clean - 3 inputs / 1 result - otherwise, lets face it, one would use a conventional calculator.
This app is ad free and you can install it on the SD card.
Hope you enjoy it. Happy time-lapses!