Pregnancy calculators provide an estimated due date with about 80% accuracy for dates within 2 weeks of the actual birth. The calculation is based on standard 40-week gestation from your last menstrual period. Early ultrasounds (before 13 weeks) can provide more precise dating, especially if your cycles are irregular.

Yes, cycle length can affect your due date calculation. The standard calculation assumes a 28-day cycle with ovulation on day 14. If your cycle is longer (e.g., 32 days), you likely ovulated later, making you less pregnant than the standard calculation suggests. Our calculator adjusts for different cycle lengths to provide a more accurate estimate.

If you don't remember your last menstrual period, your healthcare provider can estimate your due date through an early pregnancy ultrasound. The ultrasound measures the baby's size (crown-rump length) to determine gestational age. This method is most accurate when performed between 8-13 weeks of pregnancy.

Yes, early ultrasound (performed before 13 weeks) is generally more accurate than calculation based on LMP, with accuracy within 3-5 days. Ultrasound directly measures the baby's development, while LMP-based calculations assume regular cycles and standard ovulation timing. Many doctors use a combination of both methods.

Your pregnancy week is calculated from the first day of your last menstrual period. For example, if your LMP was 10 weeks ago, you are 10 weeks pregnant, even though conception likely occurred around 8 weeks ago. This gestational age system is the medical standard used worldwide.

Pregnancy is divided into three trimesters: First trimester is weeks 1-13, second trimester is weeks 14-27, and third trimester is weeks 28-40. Each trimester is approximately 13 weeks long and brings distinct developmental milestones and physical changes for both mother and baby.

Your due date may be adjusted based on early ultrasound measurements, especially if there's more than a 5-7 day difference from the LMP-calculated date. However, after the first trimester, due dates are rarely changed as later ultrasounds are less accurate for dating. The most reliable dating comes from a combination of LMP and early ultrasound.

Pregnancy is actually 40 weeks or 280 days, which equals about 9 months and 1 week. The confusion arises because months vary in length (28-31 days), while pregnancy is measured in precise weeks. Using weeks provides a more accurate and standardized way to track development and due dates across all pregnancies.