Letter Folding for Envelopes

Quote of the Day

I am a kind of paranoid in reverse. I suspect people of plotting to make me happy.

— J.D. Salinger


Figure 1: Standard #10 Business Envelope.

Figure 1: Standard #10 Business Envelope (Source).

I still occasionally write paper letters. In fact, I had some letters to write the other day, and I realized that was doing a bit of math when I folded the letters for placement into standard business envelopes that was worth discussing here. Figure 1 shows the business envelope that I normally use.

For years (i.e. decades), I folded letters into thirds by estimating where the one-third point was on the letter, folding, and hoping for the best. Sometimes, I folded letters by rolling them into a tube-shape that could be flattened for placement into an envelope (Figure 2). I still did not always get this exactly right – remember, my life is a celebration of mind-numbing detail.

Figure 1: Folding a Letter Into Thirds Using the "Tube Method".

Figure 2: Folding a Letter Into Thirds Using the "Tube Method" (Wikihow).

My Approach

I now use one of three methods:

  • For letter material that I created, I use a Word template that has very faint grey markers in margins where the fold lines need to go. Here is a link that tells you how to do this. I know that people may feel that the faint gray lines are unprofessional, but they end up in the crease and are very difficult to see (example). Here is my personal letter template.
  • For letter material that I am including in my note, I determine my fold lines one of two ways:
    • Template
      I  keep a reference sheet of paper in my cube that is exactly 1/3 the height of a sheet of letter-sized paper.
    • Origami
      I occasionally use an origami-based method (see Method 4 on this web page). It is a standard origami technique. Figure 3 proves why the origami-based method works.
Figure 4: Geometry Behind Origami Method.

Figure 3: Geometry Behind Origami Method.


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3 Responses to Letter Folding for Envelopes

  1. Peter says:

    It annoys me when anything (except of course my paystub!) is folded inwards - cos I can't see what it is! I always fold one-fold sheets outwards, and multi-fold sheets concertina-style.
    Concertina-style folding also reduces the risk that a letter in an envelope will be sliced along one of its fold lines.

    • mathscinotes says:

      Thanks for the comment. Your suggestion of concertina-style is one I had not thought about. I ended up doing some googling and finding a number of other letter-folding approaches that I never thought of – I love comments that teach me stuff. Thank you.


  2. Nick says:

    A #10 envelope has a bit of wiggle room, so the letter doesn't have to be folded in perfect thirds to fit. I take advantage of this with a fourth folding method:

    Place the envelope next to the middle of the letter to be used as a guide. Fold the bottom of the letter up so the height of the bottom "third" is a little less than the height of the envelope. Maybe 1/8th inch short. Then fold the top of the letter down over it.

    The top third will end up short, and this is on purpose. Then, holding the envelope so the opening is up and the address side facing away, put the letter in upside-down: top crease in the bottom of the envelope, back of the top third facing you.

    This way, when the envelope is opened, the recipient will grab the letter by the bottom crease to pull it out. Since the top "third" is short, their thumb will not be covering it, and the letter will naturally open itself so that they are looking at the top of the first page right away. Success.

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