Hi @BobLangdown,
Most Radzen components use rem for font-sizes. This means that the font size is relative to the font-size specified on the html element. You can globally change the font-size like this:
html {
font-size: 14px;
}
If you just want to change the DataGrid font size use your browser's developer tools to find the right selector and override it.
.rz-datatable-data td .rz-cell-data {
font-size: 14px;
}