Riddle’s Em Calculator

Riddle's Em Calculator is probably the one thing I use most in terms of web-based widgety calculators.

It's very clean, super-intuitive (give it a try, although you have already) and has some nice extras like being able to round to your choice of decimal places.

In fact it had become so much part of my work routine that when it went down the other day, I was more than a little screwed - I haven't done manual em calculations for a while, as this thing makes it so easy...