I live in the Netherlands where we too have a high tax rate. If you make an average income, 1.5x would suffice. Anything above that, 1.5x falls short. The reality is that the vast majority of freelancers stay well below 100k per year. I've adjusted the calculation to 2x to account for higher incomes and to be on the "safe" side. Thanks for your feedback!
Thanks for all your comments. My goal with this site is to get you thinking about your freelance rate / business in general, a starting point if you will. I'll be doing an iteration on the design and copy shortly.