Thanks for contacting Syncfusion support.
We suggest you to set the font-size for the “e-headercelldiv” and “e-rowcell” classes to apply the font size for the columns and headers in Grid. We have also prepared a sample based on this requirement, please download the sample from the link below,
Please add the below styles to your application,
Please get back to us if you need further assistance.
Renjith Singh Rajendran.