Period Calculator
Predict your next period, fertile window and ovulation date. Enter your last period date and average cycle length for instant results.
About This Tool
Predicts your next period start and end date, estimated ovulation date and fertile window based on your last period date and average cycle length. Also shows the next 6 predicted cycles so you can plan ahead.
Anyone wanting to predict and track their menstrual cycle. Useful for planning around events, understanding cycle patterns and general health awareness. Used by women in the UK, US, Australia, Canada, Singapore, India and worldwide.
All calculations happen entirely in your browser. No dates, health data or personal information is transmitted or stored anywhere. ToolBullet never collects your health data.
⚠️ For informational purposes only. This tool provides estimates and is not a reliable method of contraception. Cycle timing can vary. Always consult a qualified healthcare professional for medical advice. Sources: NHS, American College of Obstetricians and Gynecologists (ACOG).