Use this simple pregnancy due date calculator to estimate your baby's due date, current gestational age, and key pregnancy milestones.
How this pregnancy due date calculator works
Most due dates are estimated using obstetric dating, which starts from the first day of your last menstrual period (LMP). A typical full-term pregnancy is counted as 280 days (40 weeks) from that date. If you know your conception date instead, a common estimate is 266 days from conception.
This calculator supports both methods. It also lets you adjust for cycle length when using LMP, which can slightly shift your estimated due date.
What your estimated due date means
Your due date is a best estimate, not an exact prediction. Only a small percentage of babies are born on their exact due date. Many healthy births happen a little before or after.
- 37 to 38 weeks: Early term
- 39 to 40 weeks: Full term (most common range for planned timing)
- 41 weeks: Late term
- 42 weeks and beyond: Post-term
LMP method vs. conception date method
1) LMP (Last Menstrual Period)
This is the standard method used in most prenatal settings. It works well when menstrual cycles are predictable and the LMP date is known.
2) Known conception date
This method is useful if conception timing is known with confidence (for example, closely tracked ovulation or fertility treatment timing). It calculates from conception forward by 266 days.
Why due dates can change
During pregnancy, your care team may revise your due date based on ultrasound measurements, especially in early pregnancy. This is normal and helps improve date accuracy.
- Cycle irregularity can affect LMP-based estimates.
- Ovulation may occur earlier or later than expected.
- Early ultrasound can provide more precise developmental dating.
After calculating: next practical steps
Schedule prenatal care early
Set up your first prenatal appointment promptly if you have a positive pregnancy test. Early care supports healthier outcomes for both parent and baby.
Track milestone windows
Use your estimate to plan around major checkpoints like first-trimester screening, anatomy scan timing, maternity leave planning, and birth preparation.
Focus on healthy routines
- Take prenatal vitamins as advised (especially folic acid).
- Stay hydrated and eat nutrient-dense meals.
- Discuss safe exercise and medications with your clinician.
- Avoid smoking, alcohol, and other high-risk exposures.
Frequently asked questions
Is the calculator exact?
No. It gives an estimate based on standard dating formulas. Clinical evaluation and ultrasound are important for more personalized dating.
What if I have irregular periods?
Use the conception-date option if known, or use LMP with caution. Your prenatal provider may adjust dates after early ultrasound.
Can I use this calculator for IVF pregnancies?
IVF dating is usually based on transfer details and embryo age. This tool can give a rough estimate, but IVF-specific dating should come from your fertility team.
Final note
A pregnancy due date calculator is a helpful planning tool for appointments, milestones, and preparation. For clinical decisions, always rely on your OB-GYN, midwife, or prenatal care team.