Pregnancy Due Date & Conception Calculator
Estimate key dates for your pregnancy journey. Calculate your Estimated Due Date (EDD) based on your Last Menstrual Period (LMP) or estimate your LMP and conception window from your EDD.
Disclaimer: This calculator provides estimates only based on standard calculations. Actual ovulation, conception, and due dates can vary. Ultrasound dating is often more accurate. Always consult with your healthcare provider for medical advice and precise dating.
Select Calculation Mode
Calculate from Last Menstrual Period (LMP)
Understanding Pregnancy Dating
Estimating key dates during pregnancy helps track development and plan for arrival. Here's how this calculator works:
- Last Menstrual Period (LMP): The first day of your last period is the standard starting point for calculating pregnancy duration.
- Estimated Due Date (EDD): Typically calculated as 40 weeks (280 days) from the LMP, assuming a 28-day cycle. This calculator adjusts based on your provided average cycle length (using a modified Naegele's rule). Longer cycles push the EDD later, shorter cycles bring it earlier.
- Conception Date: Fertilization usually occurs around ovulation. Ovulation typically happens about 14 days *before* the start of the *next* expected period (or roughly LMP date + (Cycle Length - 14 days)). Since sperm can survive for a few days and the egg is viable for about 24 hours, conception is estimated within a window around the likely ovulation date.
- Gestational Age: How far along the pregnancy is, conventionally measured in weeks and days starting from the first day of the LMP.
Why are these dates estimates?
- Individual cycle lengths vary.
- The exact day of ovulation can fluctuate even in regular cycles.
- Implantation timing can vary slightly.
- Early ultrasound measurements are generally considered the most accurate method for dating a pregnancy.
This due date calculator and conception calculator provides a helpful starting point based on common calculation methods.
Note for Egypt & Globally: While calculation methods are standard, always rely on your doctor or midwife for accurate dating through clinical assessment and ultrasound, and follow local prenatal care guidelines.
Frequently Asked Questions (FAQs)
How accurate is calculating the due date from LMP?
It's a good initial estimate, especially if your cycles are regular. However, variations in ovulation timing mean it can be off by a few days or even a week or two. Ultrasound dating, particularly in the first trimester, is usually more precise.
What if I don't know my LMP or have irregular cycles?
If your LMP is unknown or cycles are very irregular, LMP-based calculation is unreliable. Dating will typically rely on early ultrasound measurements performed by your healthcare provider.
Is the conception date calculation exact?
No, it's an estimate based on average ovulation timing relative to your cycle length. Sperm viability and egg lifespan create a window of several days during which conception could have occurred.
Is gestational age the same as fetal age?
No. Gestational age is counted from the first day of the LMP (around 2 weeks *before* conception). Fetal age counts from the approximate date of conception. Gestational age is the standard used by healthcare providers (typically about 2 weeks longer than fetal age).
Does the calculator use Naegele's Rule?
It uses a modified version. Naegele's rule assumes a 28-day cycle (LMP + 7 days - 3 months + 1 year, equivalent to LMP + 280 days). This calculator starts with LMP + 280 days and then adjusts based on your provided cycle length differing from 28 days.
