I recently wrote about my “Big Edit”, during which I had the occasion to send many of my closest friends a lot of mail. Which meant I got to use a lot of 6“ x 9” envelopes.

Which made me very happy. I love the 6“ x 9” envelope.

“Oh my God, is he really going to write about how much he loves a goddamn envelope?”

Yes, yes he is.

My affection for the six-by-nine is both aesthetic and pragmatic.

The six-by-nine is a great size. Closest to the proportions of a golden rectangle than any other envelope[1].

It’s not just the proportions that are right with the six-by-nine. The color is right, too. Manila looks so much better sitting on a desk than the bleached white of other envelopes.

If you use a six-by-nine with an 8–1/2“ x 11” sheet of paper, you don’t have to wonder where to fold it. Just fold it in half. Not so with the standard envelope—with that, you’re always having to guess in thirds.

Only needing to fold once has pecuniary benefits, as well. The USPS considers any envelope up to 6–1/8“ x 11–1/2” to be a “letter.” That’s right, you can send this larger, better-looking envelope for the same price as the ubiquitous #10 envelope (9–1/2“ x 4–1/8”).

The USPS places both weight and thickness limitations on that “letter designation”. If a letter is more than 1/4“ thick, you will be paying at the ”flat“ rate rather than the ”letter" rate. That is, you may have to pay more postage on a letter in a standard envelope than in a six-by-nine simply because it is 50% thicker.

You can send more stuff for less in a six-by-nine.

The six-by-nine also sends the right message to the recipient. It’s not an often-used envelope. The #10 and the 9“ x 11” are so quotidian, so business-like. I’m a lawyer who prosecutes cases for people who have been injured by someone else’s negligence or bad faith. I pursue negligent lawyers, insurance companies, and predatory businesses. Motions to dismiss my clients’ claims arrive in 9“ x 11” envelopes. Bills and notices from Medicare arrive in #10s.

You’ll never get a bill in a six-by-nine.

What’s inside of a six-by-nine is a) casual enough for a fold but b) substantial enough for a six-by-nine.

Before you run out and buy a bunch of six-by-nines, here’s some practical advice: buy the ones without the prongs. This is my only caveat. The USPS requires the sender of any envelope containing prongs to either a) remove the prongs (this is the preferred resolution of the prong-issue) or b) tape the prongs down. If you have the option (and you do, buy the prongless six-by. Your local postal worker’s fingers thank you.

So, what’s not to love? The six-by looks better and is more practical, more fun, and easier to use.

Think about it. You’ll come around.

For an envelope with the shorter side of six inches to conform to the proportions of a golden rectangle, the longer side would need to be about 9.7 inches. ↩