Inches are evil. Fractional evil, but pure evil.

OK, the page trim is 5.5 inches in width, the left and right margins are each six-eighths of an inch, and there’s a quarter-inch gutter—quick, what is the text width?

On the other hand, if the trim width is 140 millimeters, the right and left margins are 20 millimeters each (140 – 40) and the gutter is set to 6 millimeters—quick, the text width is 94 millimeters. Piece of soup.

It is simple arithmetic versus fractions and decimals, and, well, buy a calculator.

Then you start comparing your document with a pile of open books on your desk, measuring margins, print areas, and such, and you have to stop and study your inch ruler. Are the little lines inside the inch tenths, eighths, or sixteenths of an inch? And if it is either of the latter two, your blood pressure rises as you try actually to use the measurements.

Then you have to think in fractions for everything, for boxes, columns and tables … You have a 4-1/4-inch box and you need three columns within, with a quarter-inch of margin between—how wide are the columns? Heck, you have to stop and think about how to style 4-1/4-inch in print.

Try metric: 114 millimeters minus two 6-millimeter margins equals 102 millimeters, which we divide by three … 34 millimeters per column. That’s not only an easier number to arrive at, but a simpler one to imagine or compare.

And the simpler metric figuring is true for all sorts of things: indents, tables, images, padding around text and graphics, space before and after paragraphs, how much ground coffee bean to add for a six-cup pot . . .

Give it a try. Whether you’re using Word, InDesign, Quark, or the vintage PageMaker that still runs on your garage computer (which you set up to keep score for dart tournaments), go into the options or preferences and choose millimeters as increments of measurements.

Take pleasure now in how the rulers better regulate your page and illustrate the relative size of its objects. It’s the same with pixels for a Web page or an image.

Of course, this in a land where people are measured in feet, horses in lengths, scotch in fifths, and hard alcohol content in something called proof, which compared with actual percentage lacks all level of accuracy. Oh, and two-by-fours, it turns out, are not two inches by four inches.

What? What if you’re dealing with a person or website (such as Amazon.com’s CreateSpace) that talks in inches? Simple. Jump into the preference settings and change your measurements back to inches, then hop back to millimeters when your done.

If you’re worried about holding up the person while you make the change, just ask, “Hey, what’s the print area if we use these settings?” This will give you plenty of time to change back while the person searches for a calculator needed to deal with very evil inches.