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

Oct 15, 2026

Current Cycle Day

Day 1

Legend

PeriodMenstruation days
OvulationEstimated ovulation
FertileFertile window

Predictions

Cycle 1
Period
Oct 15, 2026 – Oct 19, 2026
Ovulation
Oct 29, 2026
Fertile Window
Oct 24, 2026 – Oct 29, 2026
Cycle 2
Period
Nov 12, 2026 – Nov 16, 2026
Ovulation
Nov 26, 2026
Fertile Window
Nov 21, 2026 – Nov 26, 2026
Cycle 3
Period
Dec 10, 2026 – Dec 14, 2026
Ovulation
Dec 24, 2026
Fertile Window
Dec 19, 2026 – Dec 24, 2026
Cycle 4
Period
Jan 7, 2027 – Jan 11, 2027
Ovulation
Jan 21, 2027
Fertile Window
Jan 16, 2027 – Jan 21, 2027
Cycle 5
Period
Feb 4, 2027 – Feb 8, 2027
Ovulation
Feb 18, 2027
Fertile Window
Feb 13, 2027 – Feb 18, 2027
Cycle 6
Period
Mar 4, 2027 – Mar 8, 2027
Ovulation
Mar 18, 2027
Fertile Window
Mar 13, 2027 – Mar 18, 2027

Learn more

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

Was this useful?

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