<p><strong>En formule :</strong></p>
<pre><code class="lang-auto">=COLONNE(INDIRECT(A1&"1"))
</code></pre>
<p>(où A1 contient la lettre de colonne)</p>
<p><strong>En VBA :</strong></p>
<pre data-code-wrap="vba"><code class="lang-vba">Function LettreVersNum(lettre As String) As Long
LettreVersNum = Range(lettre & "1").Column
End Function
</code></pre>
<p><strong>En Python :</strong></p>
<pre data-code-wrap="python"><code class="lang-python">from openpyxl.utils import column_index_from_string
num = column_index_from_string('AA') # 27
</code></pre>