A general rule of thumb is: “The greater the crater, the greater the diameter of the bullet hole will be than the original nominal caliber.
For Example: (with lead bullets)
A .22 caliber may leave a .30 caliber hole.
A .38 caliber (or 9mm) may leave a .45 caliber hole.
A .45 (or .44) may leave a hole greater than one-half inch in diameter!