Choosing the right size banjo head Measure your banjo for the correct head diameter
Your banjo's rim may be slightly out of round, so take at least three diameter measurements at different points on the outside of the banjo's tone ring or rim top.
Use the average diameter to the nearest 1/16" to order the correct size.
Most modern banjos use an 11"-diameter head. Modern makers of "old-time" open-back banjos usually use 11" (and sometimes 12") heads. Vintage banjos, however, may have a range of rim diameters from 10" to 12".
Choose the correct crown height
Crown height is the vertical distance from the top of the head's mounting band to the top surface of the head.
A banjo with a flathead tone ring (or a flat-topped banjo) requires a medium or high crown head.
A banjo with an archtop tone ring requires a low crown head.
The correct crown height prevents the banjo's tension hoop from pulling down too far, and ensures the hoop won't be so high as to impede the strings.