To calculate the correct exposure equivalence based on an initial shutter speed, aperture and ISO settings.
You can use the calculator with ND filter. Determine how to make 1000 times longer photos, for example.
Two of the three parameters can be blocked, the last parameter is determined automatically.
The minimum and maximum speed can be set, it goes the same for aperture and ISO to be specific to your device.

Free version sponsored by some ads. If you want to support the development and use an ad-free version install
https://play.google.com/store/apps/details?id=com.ccl.longexposurecalculator.noad

Keywords:
photo, ND filter, long exposure, exposure calculator

Performance improvement
Advanced settings that allow you to configure all speeds, apertures and sensitivities manually.