Period
Calculator

Predict upcoming menstrual periods, ovulation dates, and fertile windows based on cycle length and last period date.

Cycle Settings

days
days

Next Period

May 31, 2026

Current Cycle Day

Day 1

Legend

PeriodMenstruation days
OvulationEstimated ovulation
FertileFertile window

Predictions

Cycle 1
Period
May 31, 2026 – Jun 4, 2026
Ovulation
Jun 14, 2026
Fertile Window
Jun 9, 2026 – Jun 14, 2026
Cycle 2
Period
Jun 28, 2026 – Jul 2, 2026
Ovulation
Jul 12, 2026
Fertile Window
Jul 7, 2026 – Jul 12, 2026
Cycle 3
Period
Jul 26, 2026 – Jul 30, 2026
Ovulation
Aug 9, 2026
Fertile Window
Aug 4, 2026 – Aug 9, 2026
Cycle 4
Period
Aug 23, 2026 – Aug 27, 2026
Ovulation
Sep 6, 2026
Fertile Window
Sep 1, 2026 – Sep 6, 2026
Cycle 5
Period
Sep 20, 2026 – Sep 24, 2026
Ovulation
Oct 4, 2026
Fertile Window
Sep 29, 2026 – Oct 4, 2026
Cycle 6
Period
Oct 18, 2026 – Oct 22, 2026
Ovulation
Nov 1, 2026
Fertile Window
Oct 27, 2026 – Nov 1, 2026

Learn more

How do cycle trackers predict ovulation, and why do cycle lengths vary?

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Frequently Asked Questions

Add your average cycle length in days to the first day of your last period to estimate the start of the next cycle. A typical cycle length is 28 days, but cycles ranging from 21 to 35 days are considered normal.

The average menstrual cycle is 28 days, measured from the first day of one period to the first day of the next. Cycle lengths between 21 and 35 days are medically considered within the normal range.

Period calculators are most accurate for people with consistent cycle lengths. Stress, illness, weight changes, and hormonal factors can shift the actual start date by several days from the prediction.

Period Calculator - Menstrual Cycle Predictor | ToolsCanvas