Pregnancy Due Date Calculator - Expected Delivery Date & Trimester
Use our free Pregnancy Due Date Calculator to estimate your baby's expected delivery date using LMP (Last Menstrual Period), conception date, or IVF transfer. See your trimester timeline, week-by-week milestones, and pregnancy progress — all in one place.
Pregnancy Due Date Calculator
Your Baby's Expected Delivery Date
Estimate your baby's due date using LMP, conception date, or IVF transfer. See trimester timeline, weekly milestones, and your pregnancy progress — all 100% free.
Due Date Calculator
Choose your input method
Enter your date and click
Calculate Due Date
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What is a Pregnancy Due Date Calculator?
A Pregnancy Due Date Calculator is a simple tool that estimates the expected delivery date of your baby. It uses standard obstetric formulas — based on your last menstrual period (LMP), conception date, or IVF transfer date — to calculate the most likely date your baby will be born. The calculator also shows your current gestational age, which trimester you're in, and key milestones for the coming weeks.
Pregnancy due dates are always an estimate. Only about 4% of babies arrive exactly on their due date. Most are born within two weeks before or after it. Due dates help your doctor schedule tests, monitor growth, and prepare for delivery — they're a planning tool, not a guarantee.
The Three Due Date Calculation Methods
| Method | Formula | Best For |
|---|---|---|
| LMP (Last Period) | LMP + 280 days (40 weeks) | Most common; assumes 28-day cycle |
| Conception Date | Conception + 266 days (38 weeks) | If you know exact ovulation/conception date |
| IVF Day-3 Transfer | Transfer + 263 days | Cleavage-stage embryo transfer |
| IVF Day-5 Transfer | Transfer + 261 days | Blastocyst transfer (most common) |
Naegele's Rule — The Standard Formula
Most pregnancy due dates are calculated using Naegele's Rule, developed by German obstetrician Franz Naegele in the 1800s. It works like this:
(OR: LMP + 1 year − 3 months + 7 days)
Example: If LMP was on January 1, 2026:
Due Date = January 1, 2026 + 280 days = October 8, 2026
This formula assumes a regular 28-day menstrual cycle with ovulation on day 14. If your cycle is longer or shorter, the calculator automatically adjusts your due date.
The Three Trimesters of Pregnancy
| Trimester | Weeks | Key Features |
|---|---|---|
| First | Weeks 1–13 | Implantation, organ formation, heartbeat detectable at ~6 weeks, morning sickness begins |
| Second | Weeks 14–27 | Baby movements felt (around 16–22 weeks), anatomy scan at 18–20 weeks, steady growth |
| Third | Weeks 28–40 | Rapid growth, brain development, baby positioning for birth, frequent checkups |
Gestational Age vs Fetal Age
These two terms are often confused. It's important to know the difference:
- Gestational Age: Counted from the first day of your last menstrual period (LMP). This is how doctors typically measure pregnancy.
- Fetal Age (Embryonic Age): Counted from the actual date of conception (ovulation). This is about 2 weeks less than gestational age.
So a "40-week" pregnancy is actually about 38 weeks of fetal development. This calculator shows both ages for clarity.
How to Use This Pregnancy Due Date Calculator
Choose Method
LMP, Conception, or IVF transfer — pick what applies to you.
Enter the Date
Enter the relevant date. For LMP, you can adjust cycle length.
View Your Due Date
See your expected delivery date, current week, trimester, and days remaining.
Track Milestones
Follow the week-by-week timeline to know what to expect each week.
Key Pregnancy Milestones & Medical Tests
- Weeks 4–5: Positive pregnancy test; implantation complete
- Weeks 6–7: First ultrasound; heartbeat may be detectable
- Weeks 8–9: First prenatal checkup; blood tests ordered
- Weeks 11–13: NT scan (Nuchal Translucency) & first-trimester screening
- Weeks 18–20: Anatomy scan (anomaly scan) — detailed check of baby's organs
- Weeks 24–28: Glucose tolerance test (GTT) to screen for gestational diabetes
- Weeks 32+: Growth scans, monitoring baby's position; more frequent checkups
- Weeks 36+: Weekly doctor visits; check for baby position (head-down)
- Weeks 37–40: Early term to full term; birth plan finalized
How Accurate Is a Due Date?
Due dates are statistical estimates. Here's what the data shows:
- Only about 4% of babies are born on their calculated due date
- Roughly 80% of babies are born within two weeks before or after the due date
- First pregnancies often go slightly longer than subsequent pregnancies
Your doctor may adjust your due date after an early ultrasound (usually at 8–13 weeks), which is more accurate than LMP-based estimates — especially if your cycle is irregular.
When Does Full-Term Begin?
The American College of Obstetricians and Gynecologists (ACOG) defines these terms:
| Term | Weeks | Notes |
|---|---|---|
| Preterm | Before 37 weeks | Requires special care; NICU admission may be needed |
| Early Term | 37–38 weeks | Acceptable but slightly higher risk of minor complications |
| Full Term | 39–40 weeks | Optimal window for birth |
| Late Term | 41 weeks | Closer monitoring; induction may be recommended |
| Post Term | 42+ weeks | Delivery usually induced to reduce risk |
Important: This Calculator Is Not Medical Advice
This pregnancy due date calculator provides estimates based on standard obstetric formulas. It cannot replace medical evaluation. Your obstetrician may adjust your due date based on:
- Early ultrasound measurements (crown-rump length, biparietal diameter)
- Your specific menstrual cycle history
- Multiple pregnancy (twins, triplets — often earlier delivery)
- Pre-existing medical conditions
- Fetal growth patterns during pregnancy
Always follow your doctor's guidance for prenatal care and delivery planning.