Due Date Calculator

Calculate pregnancy due date from last menstrual period or conception date.

This calculator provides an estimated due date only. Actual delivery dates vary significantly. Consult your obstetrician or midwife for medical dating and personalised pregnancy guidance.

Estimated Due Date

Weeks Pregnant

Trimester

Days to Go

Conception Est.

How It Works

Enter the first day of your last menstrual period (LMP) or conception date. The calculator computes the estimated due date (EDD), current gestational age, and trimester.

**Due Date Calculator — Pregnancy Planning Made Easy**

Knowing your estimated due date (EDD) is one of the first things expectant parents want to calculate. Our Due Date Calculator uses medically accepted methods to give you an accurate estimate, along with weekly milestones throughout your pregnancy journey.

**How Due Date Is Calculated**

The most widely used method is Naegele's Rule:

EDD = Last Menstrual Period (LMP) + 280 days (40 weeks)

This assumes:
- A regular 28-day cycle
- Ovulation on Day 14 of the cycle
- Pregnancy lasting exactly 40 weeks from LMP

Since fertilisation typically occurs ~2 weeks after LMP, the foetus is actually 38 weeks old at the due date.

**Alternative Calculation Methods**

1. **From Conception Date:** Add 266 days (38 weeks) to the confirmed conception or ovulation date.
2. **From IVF Transfer:** For 3-day blastocysts, add 263 days. For 5-day blastocysts, add 261 days.
3. **Ultrasound Dating:** In clinical practice, early ultrasound (6–12 weeks) is the most accurate dating method.

**Pregnancy Trimesters**

- **First Trimester:** Weeks 1–12
- **Second Trimester:** Weeks 13–27
- **Third Trimester:** Weeks 28–40 (delivery)

**What 'Due Date' Actually Means**

Only about 5% of babies are born exactly on their due date. Most births occur within 2 weeks before or after the EDD. Births between 37 and 42 weeks are considered 'term'. The EDD is an estimate, not a deadline.

**Key Pregnancy Milestones**

- Week 6: Heartbeat detectable by ultrasound
- Week 12: End of first trimester; miscarriage risk significantly decreases
- Week 20: Anatomy scan; gender typically visible
- Week 24: Viability threshold (survival outside womb possible with medical support)
- Week 37: Full term begins
- Week 40: Due date
- Week 42: Post-term; induction typically recommended

Frequently Asked Questions

The calculated EDD is an estimate based on Naegele's Rule. Only about 5% of babies are born on the exact due date. Early ultrasound dating (6–12 weeks) is the most accurate method.

Irregular cycles make LMP-based calculation less accurate. Use conception date if known, or rely on ultrasound dating from your healthcare provider.

Gestational age counts from the first day of the last menstrual period. Fetal age (conception age) counts from fertilisation — typically 2 weeks less than gestational age.

Full term is 39–40 weeks gestation. Early term is 37–38 weeks, late term is 41 weeks, and post-term is 42+ weeks.

For a 3-day embryo transfer, add 263 days from the transfer date. For a 5-day blastocyst transfer, add 261 days.