Menstrual Cycle Calculator: Find Your Training Phase
Predict your period, ovulation and the 4 phases, with a training focus for each. Built for endurance athletes.
This free menstrual cycle calculator predicts your next periods, your ovulation and fertile window, and shows which of the four cycle phases you are in today, with a training focus for each one. Enter your last period date and your usual cycle length to plan your running, cycling or swimming around your body. It is an informational estimate, not a contraception or fertility tool.
The 4 menstrual cycle phases and how to train them
Days are based on an average 28-day cycle and shift with your own cycle length.
Bleeding begins and estrogen and progesterone are at their lowest. Energy and mood can dip, though many athletes feel fine once the flow starts.
Training focus: Keep it easy. Recovery runs, mobility, technique and light aerobic work. Movement often eases cramps, so train if you feel up to it.
Estrogen rises steadily toward ovulation. Many women report higher energy, better recovery and greater tolerance for hard efforts.
Training focus: Your window for intensity. Schedule intervals, threshold work, strength and key sessions or personal bests here.
Estrogen and luteinizing hormone peak. Power output can be at its highest, but rising joint laxity may slightly raise injury risk.
Training focus: Great for peak efforts and races, but warm up well and stay technical on explosive work to protect your joints.
Progesterone rises, core temperature climbs about 0.3 to 0.5°C, and perceived effort often increases, especially in the days before your period.
Training focus: Favor steady aerobic volume and base work. Hydrate well, manage heat, and listen to your body as fatigue and PMS build.