What is the average menstrual cycle length?

The average menstrual cycle is 28 days, but normal cycles range from 21 to 35 days. Period duration averages 3–7 days.

What are the phases of the menstrual cycle?

The cycle has four phases: Menstrual (days 1–5), Follicular (days 1–13), Ovulation (day 14), and Luteal (days 15–28). The luteal phase is fairly constant at 14 days regardless of cycle length.

Menstrual Cycle Calculator – Period & Fertile Window Tracker

Menstrual Cycle Calculator

Track your menstrual cycle, predict upcoming periods, fertile windows, and ovulation dates.

First day of last period

Cycle length (days)

Period duration (days)

Cycles to show

Current phase

menstrual phase

Next period

Jul 13, 2026

Period start	Period end	Fertile window	Ovulation
Jun 15, 2026 Current	Jun 19, 2026	Jun 24, 2026–Jun 30, 2026	Jun 29, 2026
Jul 13, 2026	Jul 17, 2026	Jul 22, 2026–Jul 28, 2026	Jul 27, 2026
Aug 10, 2026	Aug 14, 2026	Aug 19, 2026–Aug 25, 2026	Aug 24, 2026
Sep 7, 2026	Sep 11, 2026	Sep 16, 2026–Sep 22, 2026	Sep 21, 2026
Oct 5, 2026	Oct 9, 2026	Oct 14, 2026–Oct 20, 2026	Oct 19, 2026
Nov 2, 2026	Nov 6, 2026	Nov 11, 2026–Nov 17, 2026	Nov 16, 2026

Predictions assume a regular cycle. Stress, illness, travel, and hormonal changes can shift ovulation timing.

Menstrual Cycle Calculator

The Menstrual Cycle Calculator predicts upcoming periods, fertile windows, and ovulation dates for up to 12 cycles ahead based on your cycle length and last period date.

Phases of the menstrual cycle

Menstrual phase: Days 1–5 (average). Uterine lining sheds.
Follicular phase: Day 1 to ovulation. Follicle develops, oestrogen rises.
Fertile window: ~5 days before ovulation + ovulation day.
Ovulation: Mid-cycle. Egg released.
Luteal phase: Ovulation to next period (always ~14 days).