Confusion in line spacing, \linespread, pt, and \titlespacing

Question

My university requires double spacing within paragraphs and triple spacing between paragraphs. It also requires triple spacing before each section heading and after the chapter title. I used:

\documentclass [12pt, a4paper, twoside, openany]{report}

...

%Triple spacing between paragraphs
\setlength\parskip{36pt}

%For double spacing, add \doublespacing after \begin{document}
\usepackage[nodisplayskipstretch]{setspace}

...

%For centering of chapter titles:
\usepackage{titlesec}
\titleformat{\chapter}[display]
{\normalfont\huge\bfseries\centering}{\chaptertitlename\ \thechapter}{1em}{\Huge}

%Change Section Headings and lower headings' font size to 12pt
\titleformat{\section}
{\normalfont\normalsize\bfseries}{\thesection}{1em}{}
\titleformat{\subsection}
{\normalfont\normalsize\bfseries}{\thesubsection}{1em}{}
\titleformat{\subsubsection}
{\normalfont\normalsize\bfseries}{\thesubsubsection}{1em}{}

%Change spacing between chapter titles and text
\titlespacing*{\chapter}{0pt}{0pt}{27pt}

%Change spacing between section titles and text
\titlespacing*{\section}{0pt}{36pt}{24pt}
\titlespacing*{\subsection}{0pt}{36pt}{24pt}
\titlespacing*{\subsubsection}{0pt}{36pt}{24pt}

Here is the output:

and

I'm confused as to what is the definition of line spacing for the document class report with a 12pt normal font. Linespread and baselineskip only add to the confusion.

From what I gathered from the internet, double spacing isn't 24 pt if the normal font is 12 pt. Also, the skip or space between lines and paragraphs is also computed differently. Please help me resolve this confusion. Thank you.

P.S. How do we remove all that unnecessary space between "Chapter #" and "Chapter Title"?

Answer 1

There is not clear definitions for double space or triple space.

See the discussion in What does 'double spacing' mean?

\baselineskip is a length command. Specifies the minimum space between the bottom of two successive lines in a paragraph.

\baselinestretch scales the value of \baselineskip. Its default value is 1.0 but its best value depends on the font its size and style, the length of the lines, and more. The standard classes of LaTeX set the \baselinestretch independently of these factors.

The package setspace puts the one-and-a-half baseline spacing to 1.5 times the font size in pt (to 18pt for a 12pt fontsize), and double-spacing as twice the font size in pt (to 24pt for a 12pt fontsize). Therefore we might define triple-baseline-spacing as three times the font size = 36pt for a 12pt font.

You can ask your university what they mean by double space and triple space: LaTeX convention or ms word? Or show them a sample printed chapter for approval before the final presentation.

As you already know, the titlesec package will help you to format the header. Using \titlespacing you can control the space before and after. You should add some negative space to counteract the effect of triple spacing between paragraphs.

Similar problems might arise with figures and tables.

With this code.

\documentclass [12pt, a4paper, twoside, openany]{report}
    
\usepackage{kantlipsum} % dummy text

\usepackage{titlesec} % added <<<<<<

\usepackage{setspace} % added <<<<<<
\doublespacing

%%%%%%%%%% chapters
\titleformat
{\chapter} % command to format
[display] % shape: hang, display, block, frame etc
{\normalfont\huge\bfseries\centering}  % format of label + chapter title
{\chaptertitlename\ \thechapter} % label "Chapter 1:"
{-2ex} % separation label - chapter title <<<<<<<<<<<<<<<<<<<<<
{} % code before

\titlespacing{\chapter}
{0pt} %left of the label + title
{-6ex plus .3ex minus .1ex } % vertical space before the title
{-1ex plus .1ex} % idem after title (in ex units + glue)


%%%%%%%%%%%%%%  sections
\titleformat{\section}
[block] % shape 
{\normalfont\large\bfseries}% format (keep the chapter font family!)
{\thesection.} % label "1.1."
{0.8ex}% separation label -  section title 
{}

\titlespacing{\section}
{0pt} %left of label + section title
{-5ex plus .3ex minus .1ex } % before the label + section title
{-5ex plus .1ex} % after 

%%%%%%%%%%%%%  subsections
\titleformat{\subsection}
[block] % shape 
{\normalfont\bfseries}% format (keep the chapter font family!)
{\thesubsection.} % label "1.1.1,"
{0.8ex}% separation label -  section title 
{}

\titlespacing{\subsection}
{0pt} %left of label + subsection title
{-5ex plus .3ex minus .1ex } % before the label + subsection title
{-5ex plus .1ex} % after 

\setlength{\parskip}{36pt} % added, triple space(?) <<<<<<<<<<<<<

\begin{document}
    
    \chapter{Computational Techniques}  
    1. \kant[1] 
    \section{Density functional theory}
    2. \kant[9]
    \subsection{Electron Density}
    3. \kant[3-5]   
 
\end{document}