ITWolfy's post in Lost already - client side logo size was marked as the answer
Hi, if you talking about the logo on the webpage, you will need to edit the header.tpl file in your template, lets say we use template six:
/home/username/public_html/templates/six/header.tpl
Find the code:
{if $assetLogoPath}
<a href="{$WEB_ROOT}/index.php" class="logo"><img src="{$assetLogoPath}" alt="{$companyname}"></a>
{else}
<a href="{$WEB_ROOT}/index.php" class="logo logo-text">{$companyname}</a>
{/if}
Replace with:
{if $assetLogoPath}
<a href="{$WEB_ROOT}/index.php"><img style="width:100%;max-width:330px;" src="{$WEB_ROOT}/templates/{$template}/img/logo.png" alt="{$companyname}" /></a>
{else}
<a href="{$WEB_ROOT}/index.php" class="logo logo-text">{$companyname}</a>
{/if}