What it does
Period Tools is a free period calculator. Enter your last period date and cycle length and it predicts your next 6 periods, your ovulation day and your most fertile window.
Why it helps
Most cycle apps want an account and a subscription for what is essentially calendar math. This gives you the same predictions instantly in the browser - no signup, no data collection, mobile-first.
Key details
- Predicts the next 6 periods
- Ovulation day and fertile window
- Instant, free, no signup, works on any phone
