Once you know the details, you can just input the data in 'Income Tax Calculators' that can be found online, such as this. Of course, precaution needs to be taken to ensure you are entering the correct details.

However, the harder part is knowing the details. Businesses may hire 'Tax Managers' to handle the taxes. Even then, you do need to put some inputs.

Learning the details for the first time may take 2-3 days. One can start with the Clear Tax website.

Note that 'Income Tax Return' is different from 'Income Tax'. On the same website you can find a Income Tax Guide. Feel free to spend 10-20 hours on that website - it is more that what we could explain.

Of course, this information is useful once you start earning yourself. Until then, you may not even want to invest much time on this task. Feel free to utilise your time elsewhere.