What this tool does
A period calculator estimates when your next period is likely to begin, based on the first day of your last period and your typical cycle length. Tracking this helps you anticipate and plan around your cycle, though every body is different and natural variation is normal.
How to use this tool
- Enter the first day of your last period.
- Enter your average cycle length in days.
- Read the estimated start date of your next period.
- Track over several months for a more accurate pattern.
Why it matters
Knowing roughly when your period is due helps with everyday planning, travel and being prepared. Tracking over time can also help you notice changes in your cycle that may be worth discussing with a health professional. This tool is an estimate, not medical advice.