# Baseline in TikZ default unit of length

Lately, I have been using the baseline argument in TikZ pictures, but I couldn't figure out what was the default unit of length. I know that the cm is the default unit for TikZ package, but it doesn't seem to be se case for baseline :

\documentclass[10pt]{article}
\usepackage{pgf,tikz}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
\pagestyle{empty}

\begin{document}

without baseline :
\begin{tikzpicture}[line cap=round,line join=round,>=triangle 45]
\clip(-1,-1) rectangle (5,5);
\draw [line width=1pt] (0,4)-- (4,4);
\draw [line width=1pt] (4,4)-- (4,0);
\draw [line width=1pt] (4,0)-- (0,0);
\draw [line width=1pt] (0,0)-- (0,4);
\end{tikzpicture}\\
with baseline (no unit) :
\begin{tikzpicture}[baseline=2, line cap=round,line join=round,>=triangle 45]
\clip(-1,-1) rectangle (5,5);
\draw [line width=1pt] (0,4)-- (4,4);
\draw [line width=1pt] (4,4)-- (4,0);
\draw [line width=1pt] (4,0)-- (0,0);
\draw [line width=1pt] (0,0)-- (0,4);
\end{tikzpicture}\\
with baseline (cm) :
\begin{tikzpicture}[baseline=2cm, line cap=round,line join=round,>=triangle 45]
\clip(-1,-1) rectangle (5,5);
\draw [line width=1pt] (0,4)-- (4,4);
\draw [line width=1pt] (4,4)-- (4,0);
\draw [line width=1pt] (4,0)-- (0,0);
\draw [line width=1pt] (0,0)-- (0,4);
\end{tikzpicture}
\end{document}


Does any one have any idea about where I could find this kind of information.

Best regards

• Coordinates may default to 1cm (see \pgfsetxvec and \pgfsetyvec), but arguments default to pt, same as normal LaTeX (except without the error message). – John Kormylo Mar 27 '18 at 17:56
• Yes, this is perhaps one of the most confusing aspects of TikZ/pgf. It also expects the arguments of sin and cos to be in degrees whereas the arguments of sinh and cosh are not. – user121799 Mar 27 '18 at 18:24
• @marmot but sinh and cosh are not really trigonometric function unlike sin and cos. For the former an argument of degree seems really odd. – Skillmon Mar 27 '18 at 21:56
• @Skillmon No, I certainly wouldn't want any function to have arguments in degrees. – user121799 Mar 27 '18 at 21:58
• @marmot me neither, but it is at least reasonable that sinh and cosh don't take their arguments in degrees while it is somewhat understandable that sin and cos do. – Skillmon Mar 28 '18 at 6:47

It seems that this is interpreted in pt:

\documentclass[10pt]{article}
\usepackage{pgf,tikz}
\usepackage{mathrsfs}
\usetikzlibrary{arrows}
\pagestyle{empty}

\begin{document}

without baseline :
\begin{tikzpicture}[line cap=round,line join=round,>=triangle 45]
\clip(-1,-1) rectangle (5,5);
\draw [line width=1pt] (0,4)-- (4,4);
\draw [line width=1pt] (4,4)-- (4,0);
\draw [line width=1pt] (4,0)-- (0,0);
\draw [line width=1pt] (0,0)-- (0,4);
\end{tikzpicture}\\
with baseline (no unit) :
\begin{tikzpicture}[baseline=2, line cap=round,line join=round,>=triangle 45]
\clip(-1,-1) rectangle (5,5);
\draw [line width=1pt] (0,4)-- (4,4);
\draw [line width=1pt] (4,4)-- (4,0);
\draw [line width=1pt] (4,0)-- (0,0);
\draw [line width=1pt] (0,0)-- (0,4);
\end{tikzpicture}\\
with baseline (pt) :
\begin{tikzpicture}[baseline=2pt, line cap=round,line join=round,>=triangle 45]
\clip(-1,-1) rectangle (5,5);
\draw [line width=1pt] (0,4)-- (4,4);
\draw [line width=1pt] (4,4)-- (4,0);
\draw [line width=1pt] (4,0)-- (0,0);
\draw [line width=1pt] (0,0)-- (0,4);
\end{tikzpicture}
\end{document}


gives identic results.

• I also noticed that. But couldn't find anything to confirm it. – IdoDaisuke Mar 27 '18 at 17:50
• @IdoDaisuke I think it is not mentioned in the pgfmanual. At least not on the first 128 pages... – Skillmon Mar 29 '18 at 18:15
• @IdoDaisuke page 132 mentions something related, I guess: If two numbers, one with a dimension and one without, are summed up, the dimensionless is considered pt. – Skillmon Mar 29 '18 at 19:05
• @IdoDaisuke the only other information about interpreting something as pt I found is: "The dimensionless units of SVG are always interpreted as points (pt)." on page 744. – Skillmon Mar 29 '18 at 19:17