--base-font-size=BASE_FONT_SIZE
:Quote from: "Calibre"The base font size in pts. All font sizes in the produced book will be rescaled based on this size. By choosing a larger size you can make the fonts in the output bigger and vice versa. By default, the base font size is chosen based on the output profile you chose.V grafickém prostředí na to určitě bude nějaký editbox.