I need a font size of 12 pt and a line spacing of 1.5 lines.
I try:
\documentclass{article}
\usepackage{lipsum}
\linespread{1.5} %regulate line spacing
\renewcommand{\normalsize}{\fontsize{12pt}{0}\selectfont}
\begin{document}
\lipsum[0]
\end{document}
I set the baseline skip in the second {} in \fontsize to 0 pt because I think it would interfere with \linespread. On the other hand \linespread appears not to work.
Can you help?

\usepackage{setspace}with\onehalfspacing? (and leave the font tampering aside, supplying it to the documentclass as an option). – gusbrs Nov 19 '18 at 22:33\fontsize{12pt}{0}specifies 12pt font on 0pt !!! baseline, so stretching the baseline by a factor of 1.5 doesn't do much..... – David Carlisle Nov 19 '18 at 22:52\fontsize{12pt}{12pt}? Do I need to include the factor 1.2? I want to benchmark the result to Microsoft Word. – Viesturs Nov 19 '18 at 22:55\fontsize{12bp}{18bp}your code has a baseline space of0*1.5=0ptso tex doesn't even try to maintain a regular baseline at all as it has impossible constraints – David Carlisle Nov 19 '18 at 22:58\baselineskipis additive - on top of the\baselineskipand additional\linespreadwould be added. – Viesturs Nov 19 '18 at 23:00