How to change width and height of Blogger top menu bar

Edit HTML of your template, [Ctrl F] search for "/* tabs"

/* Tabs
----------------------------------------------- */

.tabs-inner .widget li a {
  display: inline-block;

  padding: .6em .5em;

  font: $(tabs.font);
  color: $(tabs.text.color);

  border-$startSide: $(tabs.border.width) solid $(content.background.color);
  border-$endSide: $(tabs.bevel.border.width) solid $(tabs.border.color);

-In the code "padding" the first value [.6] is used for height and second value [1.2] is used for width-
-Decrease 1.2 to .5 and space wil shrink!-