PeriodPredict

Period Tracker

Simple, private, offline period predictions.

Last period start

Cycle length (days)

Next three period dates by cycle length

Each predicted date adds one cycle length to the previous one. All rows below start from a last period on 1 September 2026.

Cycle length	Next period	Second	Third
26 days	27 September 2026	23 October 2026	18 November 2026
28 days	29 September 2026	27 October 2026	24 November 2026
30 days	1 October 2026	31 October 2026	30 November 2026
32 days	3 October 2026	4 November 2026	6 December 2026

Predictions drift further out with each cycle because real cycle length varies by a few days month to month. Stress, illness, travel, and training load all shift it. General wellness information only, not medical advice. Discuss any health decision with a qualified clinician.

Simple math, useful planning

Projecting forward by your average cycle length from your last period's start date gives a reasonable prediction for upcoming cycles — genuinely useful for planning around travel, events, or simply reducing surprise.

Why predictions drift over time

Cycle length naturally varies month to month for most people, so predictions further into the future carry more uncertainty — treat the 2nd and 3rd projected cycles as rougher estimates than the next one.

Frequently asked questions

How do I calculate when my next period will start?

Add your average cycle length to the first day of your last period. If your last period started July 1 and your cycle is 28 days, expect the next around July 29. Track several cycles to find your average — most women's cycles are 24–35 days, with 28 being the textbook average but not the norm for everyone.

What is a normal menstrual cycle length?

Normal ranges from 21 to 35 days, with a median of 28. Cycles of 24–38 days are considered regular. Variation of ±2–5 days month to month is normal. Cycles consistently shorter than 21 or longer than 35 days, or that vary by more than 7–9 days month to month, may warrant a medical evaluation.

Why is my period late?

Common causes beyond pregnancy: stress, significant weight change, excessive exercise, illness, travel/jet lag, hormonal contraceptive changes, perimenopause (ages 40s–50s), thyroid disorders, and PCOS. A period is considered 'late' if it's more than 5 days past your expected date. Occasional late periods are very common and usually not concerning.