Your calculator says nothing about current assets.
If you have any pretax earnings, they will experience a big gain because no income tax will be due. If you sell any capital assets, you will pay no cap gains tax (stocks, homes, etc). You can also pass on your savings free of any gift tax.
There are mitigating factors, obviously, that do not appear on the calculator page. If it really is only your net position that you're interested in, these things would have to come into the analysis. If you don't include these factors, your analysis would be incomplete.
My decision is based on more than just my net position, so I don't share the view that an increase or decrease in purchasing power is a deciding factor.
We've been calling it the "billcrapulator" for a while now. Works great for those with a room temperature IQ.