Fertility & Pregnancy Calculators
Free tools to estimate your ovulation date, fertile window, next period, due date, and how far along a pregnancy is. All estimates use ACOG-cited formulas and are explained on each page.
- Ovulation CalculatorOvulation happens about 14 days before your next period starts. Your fertile window is the five days before ovulation plus the day itself â six days in total.
- Period CalculatorYour next period is due one full cycle length after the first day of your last one. This calculator projects your next two cycles.
- Safe Days CalculatorThe calendar or rhythm method estimates days outside your fertile window. It is not reliable contraception: with typical use, 12 to 24 of every 100 people relying on it become pregnant within a year.
- Menstrual Cycle CalculatorA menstrual cycle runs from the first day of one period to the first day of the next, and splits into a follicular phase before ovulation and a luteal phase after it.
- Due Date CalculatorYour estimated due date is 280 days from the first day of your last menstrual period, adjusted if your cycle is longer or shorter than 28 days.
- Pregnancy Week CalculatorPregnancy is counted in completed weeks from the first day of your last menstrual period, which means you are already counted as two weeks pregnant at conception.
- Gestational Age CalculatorGestational age is reported as completed weeks plus days, counted from the first day of the last menstrual period or from ultrasound dating.
These tools are for information only. They do not diagnose or treat, and they do not replace advice from a licensed clinician. Find an OB-GYN near you.