Why does every photo copier have a ‘reduce by 71%’ option?

Every time I touch the zoom option on any work copier it always has a “Reduce by 71%” as an option?


Let’s pull out our favorite calculator apps!  I’ll use this opertunity to tell you about my personal favorite. (FYI: I make no money on this, and have no sponsors, and don’t allow any ads.  I promote apps built by open source communities or by a single person that I think are good.). If you have Android go and get Andie Graph.  There are others, and I’m sure they’re all similar.  I just know that I have used this one through full semesters with zero problems.


If you round .70710 up you have 71%.  .070710 is the result of √.5.  Which is perfect for scaling A-sized pages down.  Making it ideal to go from an A3 to an A5 size page.

The neat thing about the A-series paper is that it has a need ratio.  If you take the largest size, A0 fold it in half then you get, two A1 prices of paper.  If you fold an A1 in half you get… Two A2’s!  It’s a neat ratio of 1:√2.   This may sound familiar as Microsoft had made a huge deal about their latest tablet supporting this ratio.   The didn’t exactly explain that it’s from the A-series paper.  We really only deal with U.S. Letter and U.S. Legal here, which BTW Legal size is the very successful iPad screen ratio.


If you’d like to get down to the real geeky math head over to between borders where they get down to the fine details.  However, the ratio should be enough to help out devs who are looking to make an app that needs such information.







Eddie Dounn

Web developer by day. Enthusiast by night. Owner of VAZED

One thought on “Why does every photo copier have a ‘reduce by 71%’ option?

  • December 24, 2015 at 5:35 pm

    I don’t think that 71% or .071 are the same as you implied. But otherwise it was good information.


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