Use this free pregnancy due date calculator to instantly find out your estimated due date, exactly how many weeks pregnant you are today, and a complete timeline of key pregnancy milestones — from your first scan all the way to full term.
This free pregnancy due date calculator works from either your last menstrual period (LMP) or your conception date — whichever you know. No email, no signup, just your due date and a full milestone timeline in seconds.
How to Use This Pregnancy Due Date Calculator
You only need one date. Choose either:
- Last menstrual period (LMP) — the first day of your last period. This is the most common method and what your OB uses.
- Conception date — if you know when you conceived, enter that instead for a slightly more precise estimate.
The pregnancy due date calculator will give you your estimated due date, your current gestational age in weeks and days, and a clickable milestone timeline showing every major pregnancy moment between now and delivery.
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Pregnancy due date calculator
Enter your last menstrual period or conception date to get your due date and key pregnancy milestones.
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How Is a Pregnancy Due Date Calculated?
The standard method used by OBs and this pregnancy due date calculator is called Naegele’s Rule — add 280 days (40 weeks) to the first day of your last menstrual period. If you know your conception date, the calculator adds 266 days instead (38 weeks from conception).
Only about 4% of babies are born on their exact due date. A normal, healthy delivery can happen anywhere between 37 and 42 weeks. Your due date is a target, not a deadline.
| Pregnancy Stage | Weeks | What’s Happening |
|---|---|---|
| First Trimester | Weeks 1–12 | Organ development, heartbeat detected around week 6 |
| Second Trimester | Weeks 13–26 | Baby moves, anatomy scan around week 20, gender reveal possible |
| Third Trimester | Weeks 27–40 | Rapid growth, baby gets into position, body prepares for labor |
| Full Term | Weeks 37–42 | Baby is fully developed — delivery can happen any time in this window |
Key Pregnancy Milestones to Know
- Week 6–8 — First prenatal visit and heartbeat confirmation ultrasound
- Week 10–13 — NIPT or first trimester screening for chromosomal conditions
- Week 18–20 — Anatomy scan (the big ultrasound); gender can usually be confirmed
- Week 24–28 — Glucose screening for gestational diabetes
- Week 35–37 — GBS swab; weekly appointments begin
- Week 39–40 — Full term; your due date window begins
Frequently Asked Questions
How accurate is a pregnancy due date calculator?
A pregnancy due date calculator based on your LMP is accurate to within 1–2 weeks for most women with regular cycles. Your OB may adjust the due date after your first ultrasound — especially if your cycles are irregular — and that adjusted date is typically more accurate.
What if I don’t know my last period date?
Use your conception date if you know it — the calculator supports both. If you don’t know either, your OB will establish a gestational age from your first ultrasound measurements, which is the most accurate method available.
Can I go into labor before my due date?
Yes — and it’s completely normal. Any birth between 37 and 42 weeks is considered full term. Births before 37 weeks are considered preterm. Your due date is the midpoint of a normal delivery window, not a hard deadline.
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