Sometimes you need to use big image files but need to display it smaller. For example this website’s logo is bigger than what i want to display:
Solution:
Add this css codes to your Custom Css section in your Theme Customizer:
#logo-img { max-height: 110px; width:auto; }
This code makes your logo will display with maximum 110px height. You can change 110 number in this code to any height you want.