Menstruation and Pregnancy Calculator

Menstruation & Pregnancy Date Calculator

Use this calculator to estimate your ovulation date, fertile window, and estimated due date based on your last menstrual period (LMP) and average cycle length. It can also estimate your current gestational age.

Understanding Your Cycle and Pregnancy Dates

Understanding your menstrual cycle is key to family planning, whether you're trying to conceive or simply tracking your health. This calculator provides estimates for important dates related to menstruation and potential pregnancy.

Last Menstrual Period (LMP)

The first day of your Last Menstrual Period (LMP) is the starting point for most pregnancy and ovulation calculations. It's considered "Day 1" of your cycle and is used to determine gestational age and estimated due date.

Average Cycle Length

Your average cycle length is the number of days from the first day of one period to the first day of your next period. While 28 days is often cited as average, cycle lengths can vary significantly from person to person (typically 21-35 days). Knowing your average helps in more accurately predicting ovulation.

Estimated Ovulation Date

Ovulation is when a mature egg is released from the ovary, making it available for fertilization. This typically occurs about 14 days before the start of your next period. For a 28-day cycle, this would be around day 14. For a 30-day cycle, it would be around day 16. Our calculator uses your average cycle length to estimate this date.

Fertile Window

The fertile window is the period during which intercourse is most likely to result in pregnancy. Sperm can live for up to 5 days in the female reproductive tract, and an egg is viable for about 12-24 hours after ovulation. Therefore, the fertile window typically spans about 5 days before ovulation, the day of ovulation, and the day after ovulation. This calculator provides an estimated 7-day fertile window.

Estimated Due Date (EDD)

The Estimated Due Date (EDD), also known as the Estimated Date of Confinement (EDC), is calculated using Naegele's Rule. This rule adds 280 days (40 weeks) to the first day of your LMP. It's important to remember that only about 4% of babies are born exactly on their due date; most arrive within a week or two before or after.

Current Gestational Age

Gestational age refers to how far along a pregnancy is, measured from the first day of the LMP. This calculator estimates your current gestational age in weeks and days, providing a snapshot of your pregnancy progression relative to today's date.

Important Considerations

• These are estimates: All dates provided by this calculator are estimates. Actual ovulation and due dates can vary due to individual biological differences, irregular cycles, or other factors.
• Consult a healthcare professional: For precise dating and personalized advice, always consult with your doctor or a healthcare provider. Ultrasounds can provide more accurate dating, especially in early pregnancy.
• Irregular Cycles: If you have highly irregular menstrual cycles, these calculations may be less accurate.

Example Calculation:

Let's say your Last Menstrual Period (LMP) started on January 1, 2024, and your average cycle length is 28 days.

• Estimated Ovulation Date: January 1 + (28 – 14) days = January 1 + 14 days = January 15, 2024.
• Estimated Fertile Window: 5 days before ovulation to 1 day after ovulation. So, January 10, 2024, to January 16, 2024.
• Estimated Due Date (EDD): January 1 + 280 days = October 8, 2024.
• Current Gestational Age (if today is March 1, 2024): Days between Jan 1 and Mar 1 = 60 days. 60 days / 7 = 8 weeks and 4 days.