一個ATM Cell的大小是固定為53 bytes (48 bytes為Data，5 bytes為Payload) ，約只有90.5%的檔案傳輸效率(48/53=0.90)
64Kbit=64bit*1024=65536bits=65536bits/8=8192Bytes=8192Bytes/53=154 Cell
常用頻寬換算對照表
64 Kbit=154 cell
128 Kbit=309 cell
256 Kbit=618 cell
384 Kbit=927 cell
512 Kbit=1236 cell
640 Kbit=1545 cell
1024 Kbit=2473 cell
2048 Kbit=4946 cell
3096 Kbit=7477 cell
8192 Kbit=19784 cell