Corncob dictionary (58k english words):
Passphrase entropy:
Comparison with random passwords, lower/upper case + digits: pwgen -sn 6 27.1 bits pwgen -sn 8 36.6 bits pwgen -sn 10 48.5 bits pwgen -sn 12 58.8 bits pwgen -sn 14 72.2 bits pwgen -sn 15 75.2 bits pwgen -sn 16 83.5 bits pwgen -sn 18 95.2 bits pwgen -sn 20 104.1 bits pwgen -sn 25 130.0 bits