Real 1GB = 1,073,741,824 Bytes
Advertised 1GB = 1,000,000,000 Bytes = ~953.67 MB
Loss total = 73,741,824 Bytes = ~70.32 MB
Real 100GB = 107,374,182,400 Bytes
Advertised 100GB = 100,000,000,000 Bytes = ~93.13 GB
Loss total = 7,374,182,400 Bytes = ~6.87 GB
Real 1TB = 1,099,511,627,776 Bytes
Advertised 1TB = 1,000,000,000,000 Bytes = ~931.32 GB
Loss total = 99,511,627,776 Bytes = ~92.68 GB
Real 1PB (that's 1024TB) = 1,125,899,906,842,624 Bytes. And if we're still using the same system by then...
Advertised 1PB = 1,000,000,000,000,000 Bytes = 909.5 TB
Loss total = 125,899,906,842,624 Bytes = 114.51 TB = 117,253.43 GB
Hard drive makers really have to get their crap together about this, or eventually we're going to be buying petabyte HDs with 114 TB missing.