Ceiling in LaTeX

You should read some guides (starter guides) for LaTeX and math (especially about the sizes). With the knowledge about them you could easily adapt to this (\bigg):

\documentclass{article}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{mathtools}
\DeclarePairedDelimiter{\ceil}{\lceil}{\rceil}
\begin{document}
\begin{equation}
\ceil[\bigg]{\frac{\log{(1-P_{0})}}{\log{(1-p)}}}
\end{equation}
\end{document}

Very simple, you can work with the asterisk.

\documentclass{memoir}

\usepackage{amsmath,amsfonts,amssymb}
\usepackage{mathtools}
\DeclarePairedDelimiter{\ceil}{\lceil}{\rceil}

\begin{document}

\begin{align}
    \ceil*{\frac{\log (1-P_{0})}{\log (1-p)}}
\end{align}

\end{document}

I also applied some minor improvements on log vs \log.

Please consider the manual http://www.ctan.org/pkg/mathtools .

Just for adding some informal tags: Kenneth Eugene Iverson floor ceiling notation.