TextMesh.fontSize

Description

The font size to use (for dynamic fonts).

If this is set to a non-zero value, the font size specified in the font importer is overriden with a custom size. This is only supported for fonts set to use dynamic font rendering. Other fonts will always use the default font size.

using UnityEngine;

public class Example : MonoBehaviour
{
    void Start()
    {
        GetComponent<TextMesh>().fontSize = 12;
    }
}