\documentclass{standalone}

\begin{document}
\begin{tabular}{|l
                |c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c|c
                |c|c|c|c|}
                \hline
                Buchstabe&
                \multicolumn{8}{c|}{K}&
                \multicolumn{8}{c|}{B}&
                \multicolumn{8}{c|}{W}\\
                \hline
                Dezimal&
                \multicolumn{8}{c|}{75}&
                \multicolumn{8}{c|}{66}&
                \multicolumn{8}{c|}{87}\\
                \hline
                Binär&0&1&0&0&1&0&1&1&
                      0&1&0&0&0&0&1&0&
                      0&1&0&1&0&1&1&1\\
                \hline
                Dezimal&
                \multicolumn{6}{c|}{18}&
                \multicolumn{6}{c|}{52}&
                \multicolumn{6}{c|}{9}&
                \multicolumn{6}{c|}{23}\\
                \hline
                Base64&
                \multicolumn{6}{c|}{S}&
                \multicolumn{6}{c|}{0}&
                \multicolumn{6}{c|}{J}&
                \multicolumn{6}{c|}{X}\\
                \hline
\end{tabular}
\end{document}