Ovulation calculator
Published On: 25/02/2026
Ovulation Calculator
Estimate your ovulation date and fertile window based on the first day of your last period and your average cycle length. This is an estimate and works best for regular cycles.
Inputs explained:
• First day of last period: the start date of your most recent menstrual period (Cycle Day 1).
• Average cycle length: number of days from one period start to the next (commonly 21–35).
• Luteal phase length (optional): days from ovulation to the next period (often ~14).
The calculator estimates ovulation as: Ovulation = Next period start − luteal phase.
• First day of last period: the start date of your most recent menstrual period (Cycle Day 1).
• Average cycle length: number of days from one period start to the next (commonly 21–35).
• Luteal phase length (optional): days from ovulation to the next period (often ~14).
The calculator estimates ovulation as: Ovulation = Next period start − luteal phase.
Typical range: 21–35 days.
If unsure, use 14.
Used only to show an estimated period range.
Important: This tool provides an estimate only. Ovulation timing can vary month-to-month. For higher accuracy, consider tracking basal body temperature (BBT), cervical mucus, or using ovulation test strips. If you’re trying to conceive or avoid pregnancy, a healthcare professional can help you choose the right method.
Ovulation Calculator — Description
The Ovulation Calculator estimates your ovulation date and fertile window using the first day of your last menstrual period (LMP) and your average cycle length. It also estimates the start of your next period and shows a simple snapshot of upcoming days. Because cycles can vary, the results should be treated as an estimate rather than a medical prediction.
For improved accuracy, consider combining calendar estimates with ovulation test strips, basal body temperature (BBT) tracking, and/or guidance from a healthcare professional.