Fit label name to button

I have no idea if this is the right approach, but here are my thoughts.

I want the label of a button to fill the width of the button. The buttons and labels are generated dynamically and are in a panel with layout set to vertical.

I probably went waaaay too complicated, as I was trying something like this in the css

font-size: #{@{this.label}.length} *do some math here* px;

which was actually pretty cool and I'm sure with some math wizardry, I could set the right size depending on how long the label is...which might be a nice exercise in learning javascript...but there is most likely a simple one liner to easily fit the label to the button. As yet, I've not been able to find it. I've tried various viewport things, but no luck so far.

Unfortunately there's no magic css property to do that !