If you create a chart using Family Tree Builder software:
Click on the 'Options button' above the chart view. In the window that opens you can use various tabs to edit the chart look according to your preferences.
By clicking on the Fonts tab, you will be able to update the font size of your chart.
If you create a chart on your online website:
Click on the ‘Advanced customization options’, to choose from the advanced editing options available for your chart.
There you can edit font sizes used along with size of the photos, the box and chart frames, and the facts shown in the chart.
