Time to crack 1Password passphrases by number of words in the passphrase:
- 3: 2 days, 17 hours
- 4: 58 years
- 5: 449,528 years
- 6: 3.5 billion years
- 7: 27 trillion years
1Password uses PBKDF2 to achieve this. They recommended four or five words per passphrase in 2013.