I encountered this very thing when I was considering leaving the office and working for myself. I wanted to understand what would be left after all the taxes, and whether it was even worth it. I tried a couple of services, but only salary calculation Latvia gave a more or less clear picture: you can compare how much you earn as an employee and as a self-employed person, taking into account mandatory contributions and income tax. Of course, it's not the absolute truth, but the figures were pretty close to what a friend's accountant later confirmed, so it's perfectly adequate for a first calculation.