Health & Lifestyle
Sleep cycles, password entropy and lifestyle calculators.
Sleep Cycle Bedtime & Wake Calculator
Bedtime and wake-up times aligned to 90-minute sleep cycles, accounting for fall-asleep latency.
Password Strength & Entropy Calculator
Calculate password entropy in bits and estimated brute-force time across attacker capabilities.
Bra Size Converter (UK / US / EU / AU / JP)
Convert bra sizes between UK, US, EU, AU and JP systems with sister sizes when band/cup doesn't fit.
Shoe Size Converter (US / UK / EU / JP / CN)
Convert shoe sizes between US, UK, EU, Japanese cm and Chinese systems for men, women and kids.
What these tools are for
Sleep cycle timing works on a simple premise: sleep runs in roughly 90-minute cycles, and waking at the end of one feels better than waking mid-cycle. The premise is sound and the precision is not — real cycles vary between people and across a night, so a suggested wake time is a target to aim near rather than an alarm to trust to the minute.
Password entropy is the opposite kind of estimate: it is exact, but only about the thing it measures. Entropy quantifies how large the search space is *given how the password was generated*, which is why a random 12-character string and a memorable one that merely looks similar are not remotely equivalent. Any password that came out of a human brain has far less entropy than its character count implies.
Nothing here is medical advice, and the tools that touch health are estimates from population averages rather than assessments of you.
Which one do I want?
- Choosing a bedtime or alarm
- Sleep cycle calculator.
- Judging password strength
- Password entropy — and generate randomly rather than inventing.