A familiar situation
Project the next expected period from an average cycle length for calendar tracking.
How to use this calculator
- Enter first day of last period, usual cycle length.
- Select Calculate to see the answer and its breakdown.
- Keep a scenario, change an input and compare the results.
Use consistent units and check the assumptions below before applying the result.
How period is calculated
Next period = LMP + cycle length. Estimated ovulation is about 14 days before that date; the fertile window is approximated from five days before to one day after ovulation. With a 29-day cycle beginning April 1, the next period is projected around April 30.
Next expected period=LMP+average cycle length.With a 29-day cycle beginning April 1, the next period is projected around April 30.
Assumptions & useful context
Not contraception or a diagnosis; seek clinical advice for concerning symptoms.
Health calculations are estimates for education. They cannot diagnose a condition or replace a clinician’s assessment. Individual needs vary, especially during pregnancy, illness and growth.
Frequently asked questions
Can I rely on this to avoid pregnancy?
No. Calendar tracking alone is not reliable contraception.
When should a clinician assess irregular periods?
Seek individualized advice for persistent changes, unusually heavy bleeding, pain, or concern.