Hi Rik and autumnus,

Sorry for my late reply, but thank you very much for your suggestions on this topic.
Your calculations are very complicated I think.
However, the type area is not the end of the story.
Unfortunately, the line length remains the same with your suggestions, even if the font size is reduced. For good readability, however, the number of characters in the line should remain more or less constant and not increase.
In any case, that's what I've read.
I have therefore orientated myself on this:
https://wiki.contextgarden.net/Introduction/From_LaTeX_to_ConTeXt/KOMA-scrartcl_Type_Area

It looks like this for me now:

\definebodyfontenvironment[12pt][interlinespace=15pt]
\setupbodyfont[libertinus, 12pt]

\setuppagenumbering[location={footer,middle}, alternative=doublesided]

\setupindenting[yes, small, next]

%\enablemode[BCOR]
% Set binding correction value .
\doifmodeelse{BCOR}{\def\bindingcorr{5mm}}{\def\bindingcorr{0pt}}

% Set visible page width.
\newdimen\PageWidth \PageWidth=\dimexpr(\paperwidth-\bindingcorr)

% Determine the paper aspect ratio.
\edef\Ratio{0.618}             %Golden Ratio

% Set the textarea height proportional to the width.
\newdimen\Height \Height=41\baselineskip            % constant number of lines (41)
\newdimen\Width \Width=\dimexpr(\Ratio\Height)

% Set the margin/gutter widths to be equal on a full spread.
%\newdimen\Back \Back=\dimexpr(((\PageWidth - \Width) / 2) + \bindingcorr)

\enablemode[oneside]
\newdimen\Back
\doifmodeelse{oneside}
    {\Back=\dimexpr(((\PageWidth - \Width) / 2) + \bindingcorr)}
    {\Back=\dimexpr(((\PageWidth - \Width) / 3) + \bindingcorr)}

% Set the top and bottom margins in a 1:2 ratio, ignoring headers.
\edef\Top{\the\dimexpr((\paperheight - \Height) / 3 - 3\lineheight)}

% Redefine \Height to include header and footer space.
\Height=\dimexpr(\Height + 8\lineheight)

% Set up the page layout using the calculated parameters.
\setuplayout[
     backspace=\the\Back,
     height=\the\Height,
     width=\the\Width,
     header=2.5\lineheight,
     headerdistance=0.5\lineheight,
     footer=4.5\lineheight,
     footerdistance=0.5\lineheight,
     bottom=2\lineheight,
     bottomdistance=0.5\lineheight,
     margindistance=0.2\lineheight,
     topspace=\Top,
     grid=on,
     ]

\starttext

\showgrid

\input knuth

\input tufte

\input knuth

\input tufte

\showlayout[1, pt, mm]

\stoptext

If I am wrong, please correct me.

Greetings
Thomas

Am 24.02.25 um 19:33 schrieb Rik Kabel:

On 2025-02-24 04:19, Thomas Meyer wrote:

Hello Hraban,

thanks for your tip.
Hopefully I'll find time to have a look at it after that busy weekend.

Regards
Thomas

Am 22.02.25 um 19:11 schrieb Henning Hraban Ramm:

Am 22.02.25 um 18:36 schrieb Thomas Meyer:

Thank you Wolfgang,

I guess I'm thinking too complicated. Ultimately, this should result in a type area according to the golden ratio.
(textheight = 660 pt = 1.618 * textwidth or something similar, depending on the font size or interlinespace)

To simplify your code, you can replace many of these measures with units, e.g. th, tw; see also lowlevel-registers.pdf

Perhaps this can help. It works for me. It lays out his page 155 (1st edition paperback) bottom page, which has a 1.7 ratio type area on a 1.5 ratio page.

\doifmodeelse{frame}{\def\Paper{letter}}{\def\Paper{octavo}}
\definepapersize [octavo]
                   [width=6in,%   152.4mm, 433.62pt, 432bp
                    height=9in]% 228.6mm, 650..43pt, 648bp
\setuppapersize[octavo][\Paper]
\setuplayout   [
%Bringhurst example on p155
%
% P = 1.5 (h=9", w=6") (648bp × 432bp) (54pc × 36pc)
% T = 1.7 (d=6.8", m=4") (491.44pt × 289.08pt) (489.6bp × 288bp) (40.8pc × 24pc)
%        (exclusive of running heads and folios)
% s = t = w/9 = 0.667" backspace and top margin
% e = 2s = 1.333" foredge
% ( f = h - t - d = 9" - 0.667" - 6.8" = 1.533"
%   but must allow for footer/footerdistance in that )
% 36 lines @ 13.5pt = 486pt, 36 lines @ 13.45bp = 484.2bp
      %
      % Bringhurst calculations for 24pica width   char/line
      %    libertinus alphabet width 10pt:   122pt   66
      %    libertinus alphabet width 10.5pt: 128pt   63
      %    libertinus alphabet width 11pt:   134pt   61
      %    libertinus alphabet width 12pt:   146pt   56
% backspace = leftedge+leftedgedistance+leftmarginwidth+leftmargindistance
% cutspace = right...
% s = w/9 = leftmarginwidth+leftmargindistance = 0.667" = 48bp
% t = s = topspace + header+headerdistance
%         header+headerdistance = 27bp
%         topspace = 48bp - 27bp = 21bp
% e = 2×s = rightmarginwidth+rightmargindistance = 1.333" = 96bp
                  vz=2,
                  location=middle,
                  backspace=pw / 9,
                  cutspace=\backspace * 2,
                  width=\backspace * 6,
                  height=(\backspace * 6 * 1.7) + (4 * \lineheight),
                  topspace=\backspace - 2 * \lineheight,
                  headerdistance=\lineheight,    header=\lineheight,
                  footerdistance=\lineheight,    footer=\lineheight,
                  leftmargindistance=8bp,   rightmargindistance=8bp,
                  leftmargin=\backspace - \leftmargindistance,
                  rightmargin=\cutspace - \rightmargindistance,
                 ]

--
Rik
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