For the interactive calculator, open the full CalcHealth page.
Open Full CalculatorFrequently Asked Questions
How accurate is a period calculator?
For regular cycles (21–35 days), predictions are accurate within 1–2 days. Stress, illness, or hormonal changes can shift timing.
What if my cycle is irregular?
Track 3+ cycles and use the average length for better accuracy.
Can I use this to avoid pregnancy?
This calculator is not a contraceptive method. Consult a doctor for birth control advice.