How to remove auto padding of FAB button in android?

just add this in your dimens.xml file

<dimen name="design_fab_image_size" tools:override="true">36dp</dimen>

This might not work for 3rd party libraries.

You can changethe attribute app:maxImageSize to match the size of your image.

app:maxImageSize="the wanted size"

I find the solution safer the the overriding of the design_fab_image_size because if your app have several floating action buttons, you will only alter one.