To set font size with pixels, use the px unit, with the font-size property. You can try to run the following code to set font size with pixels
Example
<!DOCTYPE html> <html> <head> <style> h1 { font-size: 30px; } </style> </head> <body> <h1>This is demo heading</h1> <p>This is demo text.</p> </body> </html>