I am working on The Knitting Guild of America's Master Hand Knitter course right now, which basically involves knitting swatch after swatch after swatch after swatch after ... well, you get the idea. It's a shipload of swatches.
Swatches 1, 2, 3, and 14 have to be knit on the same needles, using the same yarn so that you can compare the stitch and row gauge of different pattern stitches. (For those of you who don't knit, that means how many stitches and how many rows it takes to fill a specific measurement, i.e.; 4 stitches to the inch.)
In order to be as specific as possible, you've got to measure to an eighth of an inch, then divide that into how many stitches or rows you've knit. You wind up getting a number with a gazillion decimal places. Then you've got to multiply that number by either 18 or 10, to determine how many stitches you'd need to make an 18" wide sweater piece, or how many rows you would have to knit to make your knitting 10 inches high.
I don't know about you, but multiplying 6.288888x18 is not my idea of a fun mental exercise. Ergo (I just love that word!), my calculator has become my new BFF. And seeing as how I'm only on Level I of three levels, I suspect the two of us will be joined at the hip for a long, long time.