# Left align equation in equation enviroment

I would like to left align a set of equation like this:

$$C_{DLP}=C_{Pre-processing}+C_{Production}+C_{Material}+C_{Post-processing}+C_{Overhead}$$
$Where$
$$C_{Pre-processing}= C_O \times T_{SW}$$

$$C_{Production}= C_M \times T_{B}$$

$$C_{Material}= C_{M_kg} \times V$$

$$C_{Post-processing}= C_O \times T_{Post-processing}$$

$$C_{Overhead}= C_{El} + C_{Sr} + C_{Me}$$


How can I do it?

• Giving the fleqn option to the documentclass ? – Jérôme Dequeker Nov 21 '16 at 9:50

To left-align all equations, use the fleqn option of amsmath. If you want only a group of equations to be left-aligned, you can use the fleqn environment of nccmath, which works like the subequations environment. It accepts an optional argument to specify the left margin of the environment. I took the liberty to set most indices in text mode, as semantically they're texts:

\documentclass{article}
\usepackage{mathtools, nccmath}
\usepackage[showframe]{geometry}%

\begin{document}

\begin{fleqn}[\parindent]
\begin{subequations}
\begin{align}
& C_\mathrm{Pre-processing}= C_O × T_{SW} \\
& C_\mathrm{Production}= C_M × T_{B} \\\
& C_\mathrm{Material}= C_\mathrm{M_{kg}} × V
\end{align}
\end{subequations}
\end{fleqn}
\vspace{4ex}
\begin{gather}
C_\mathrm{Post-processing}= C_O × T_\text{Post-processing}\\
C_\mathrm{Overhead}= C_\mathrm{El} + C_\mathrm{Sr} + C_\mathrm{Me}
\end{gather}

\end{document}


• I am trying to label those equation to reference them but the label that get printed doesn't follow the equation numbering... How can it be solved? – Alexis Charalambis Nov 24 '16 at 9:40

If you do not left align the rest of your document's equations, I would not start this just for this case. I would recommend to use align as shown many times on this site.

% arara: pdflatex

\documentclass{article}
\usepackage{mathtools}

\begin{document}
\begin{align}
\begin{split}
C_{\text{DLP}}&=C_{\text{Pre-processing}} + C_{\text{Production}} \\