There's FOMO about not going out on Saturday, and then there's FOMO about not being a billionaire.

The website extremefomo.com accurately chose its name. The site lets you easily see exactly how rich you could have been if only you'd actually followed through on buying stock in Apple 15 years ago.

It's possible to figure out these depressing numbers on your own, but the site makes it easy for you to indulge your self-punishing fantasies.

All you have to do is enter the amount of money you could have invested, the name of the stock you could have invested in, and the date you could have invested on, and the site shows you exactly what you missed out on. You can only check your missed fortune going back 17 years, or to investments starting in 2000.

For example, you can see what would have happened if you'd invested in Facebook on its IPO day in 2012.

Image: screenshot/extremefomo

Image: SCREENSHOT/EXTREMEFOMO

Not too shabby, especially for a botched IPO.

You can also use the site to see investments you did well to avoid. Like Snap Inc.'s March IPO, which hasn't gone too well so far.

You can play with the site and find out what you missed out on—good or bad—here.