You can do a monte carlo simulation in a spreadsheet without a plugin, too. For each of the inputs, create a column where the cell retrieves a random value acco

You can do a monte carlo simulation in a spreadsheet without a plugin, too. For each of the inputs, create a column where the cell retrieves a random value according to the probability distribution you pick. Then, drag down 1000 rows or 10000 rows or whatever, and finally calculate percentiles based off of the outputs of each row. A few years ago when I met my now-wife, I was paying a mortgage and she was paying rent, and we wanted to get an idea of what we could afford if we wanted to stick with the budget were were already comfortable with. So the inputs were the possible sale price of my house, the possible interest rate of the new mortgage, etc. We experienced what the article describes; while we were quite conservative about each of all of those elements, the 99th percentile was a lot less conservative than the worst-case scenario of each and every input we plugged in, and it gave us an accurate target of what kind of home price we felt we could actually afford.