Pregnancy Calculator
Calculate your due date and current pregnancy week. Enter your last menstrual period date to get accurate pregnancy information.
How the Pregnancy Calculator Works
Our pregnancy calculator uses Naegele's rule, the standard method used by healthcare providers worldwide, to calculate your estimated due date. The calculation is based on the assumption that pregnancy lasts 40 weeks (280 days) from the first day of your last menstrual period.
- Naegele's Rule: Start with the first day of your last menstrual period, add 7 days, subtract 3 months, and add 1 year. This formula assumes a 28-day cycle and ovulation on day 14.
- Pregnancy Week Calculation: The calculator determines which week of pregnancy you're currently in by calculating the number of weeks since your LMP date.
- Trimester Tracking: Pregnancy is divided into three trimesters: First (weeks 1-13), Second (weeks 14-27), and Third (weeks 28-40). The calculator shows your current trimester.
- Cycle Length Adjustment: If your menstrual cycle differs from 28 days, you can adjust the cycle length for improved accuracy, though early ultrasound dating is most precise.
While due dates are estimates (only about 5% of babies are born exactly on their due date), they provide valuable guidance for planning prenatal care, scheduling appointments, and preparing for your baby's arrival. Most babies are born within two weeks before or after the calculated due date.
Common Use Cases for Pregnancy Calculation
📅 Early Pregnancy Planning
Calculate your due date early in pregnancy to plan prenatal care, schedule appointments, and understand your pregnancy timeline. One of the first questions healthcare providers ask.
💼 Maternity Leave Planning
Knowing your due date helps plan maternity leave, coordinate with employers, and ensure adequate time off. Essential for financial planning and work-life balance.
🎉 Baby Shower Planning
Due dates help friends and family plan baby showers, gender reveals, and other celebrations. Planning before the due date ensures the expecting mother can fully participate.
🏠 Home Preparation
Understanding your due date timeline helps prepare the nursery, purchase baby supplies, and complete home preparations. Reduces stress and ensures readiness.
🏥 Medical Appointment Scheduling
Healthcare providers use due dates to schedule prenatal appointments, screenings, and tests at appropriate times. Accurate due dates ensure optimal care timing.
👨👩👧👦 Family Planning
Due dates help family members plan visits, coordinate support, and prepare for the new arrival. Especially important for out-of-town family members planning travel.
Tips & Best Practices
For the most accurate due date, know the exact first day of your last menstrual period. If you're unsure, estimate as closely as possible, but remember that accuracy improves with precise LMP dates.
If your menstrual cycle is consistently longer or shorter than 28 days, adjust the cycle length in our calculator. This can improve due date accuracy for women with irregular cycles.
Always confirm your calculated due date with healthcare providers. They may adjust it based on ultrasound measurements, especially early ultrasounds which are most accurate for dating pregnancies.
When planning, consider a range around your due date (typically 2 weeks before to 2 weeks after). This ensures you're prepared for early or late arrivals.