Period Calculator

Predict your next periods and identify your fertile windows based on your cycle.

First Day of Last Period

Cycle Length (days)

Period Duration (days)

Cycles to Predict

Daily nutrition made simple — vitamins, probiotics & adaptogens in one scoop.

How it works

This calculator uses the calendar method: your next period starts after your cycle length. Ovulation occurs approximately 14 days before your next period. The fertile window spans the 5 days before ovulation and ovulation day itself.

Period Calculator: Predict Your Next Period & Fertile Days →

Understand your menstrual cycle: 4 phases, cycle length, irregularities and tracking benefits. Free period calculator included.