Overview

Estimate your ovulation date and fertile window based on your menstrual cycle. Ovulation typically occurs about 14 days before the next expected period, and the fertile window spans approximately 5–6 days around ovulation. This calculator is a reference tool and is not recommended as a sole method of contraception.

Formula

Estimated Ovulation Day = Next Period Date - 14 days
Fertile Window Start = Ovulation Day - 5 days (accounting for sperm survival)
Fertile Window End = Ovulation Day + 1 day (accounting for egg survival)

Next Period Date = Last Period Start + Average Cycle Length

How to Use

1. 1Select the first day of your last menstrual period.
2. 2Enter your average cycle length (default: 28 days).
3. 3Click the 'Calculate' button.
4. 4Your estimated ovulation date, fertile window, and next period date will be displayed.

Tips

• ✔Ovulation predictor kits (OPKs) detect the LH surge that occurs 24–48 hours before ovulation.
• ✔Basal body temperature (BBT) rises by 0.2–0.5°C after ovulation; daily tracking helps identify your pattern.
• ✔Stress, sleep changes, and weight fluctuations can shift your ovulation date.
• ✔This calculator is not a substitute for contraception. Consult your doctor if birth control is needed.
• ✔If trying to conceive, intercourse every other day during the fertile window is generally recommended.

FAQ