It depends on your computer and how you use it.

Different laptops have different battery capacities, larger or smaller screens, variable disks, more or less energy-efficient processors, and depending on whether you're online, local, watching videos, whether the screen lighting is stronger or weaker, whether you have more or less power.It also depends on whether you're online, locally, watching videos, whether the screen lighting is brighter or dimmer, whether you have more or fewer peripherals connected, etc., all this has an impact on battery consumption.

Generally speaking, you can extrapolate by averaging your current battery consumption and extrapolating by adding the capacity of the powerbank.