Accurate Due Date Calculator – Precise Pregnancy EDD by LMP, IVF & Ultrasound
Use this accurate due date calculator to find your baby's estimated arrival date. Choose from five precise methods — last period, conception, intercourse, IVF transfer, or ultrasound. See your current pregnancy week, trimester, baby's approximate size, and a birth probability calendar. No sign‑up required — all calculations run privately in your browser.
How to Get an Accurate Due Date – The Complete Guide
This accurate due date calculator gives you a reliable estimate of your baby's arrival based on the same formulas used by OB/GYNs. It supports five different calculation methods so you can pick the one that matches the information you have. Whether you know your last period, the date of conception, your embryo transfer day, or your ultrasound gestational age, this tool delivers a precise estimated due date (EDD) in seconds — all within your browser.
How Each Calculation Method Works
- Last Menstrual Period (LMP) — Naegele's Rule. Adds 280 days (40 weeks) to the first day of your last period, then adjusts for your cycle length. If your cycle is longer than 28 days, the due date moves forward; if shorter, it moves back. This is the standard method used by most OB/GYNs and provides a clinically accurate due date from LMP.
- Conception Date. A full‑term pregnancy lasts about 266 days from conception. If you know your ovulation date or the exact day you conceived, this method gives you a very accurate due date based on conception.
- Intercourse Date. Since sperm can survive up to 5 days, the intercourse date isn't the same as the conception date. We estimate conception 2 days after intercourse, then add 266 days for a reasonable due date from intercourse estimate.
- IVF Transfer. This is the most precise method. For a Day 3 embryo transfer, 263 days are added; for a Day 5 blastocyst, 261 days are added. This IVF accurate due date calculator reflects the exact embryo age.
- Ultrasound. An early first‑trimester ultrasound measures the baby's crown‑rump length to determine gestational age within a few days. Enter the ultrasound date and the measured gestational age (weeks + days), and the calculator works backward to find the due date — giving you the most accurate pregnancy due date from ultrasound.
Why Use This Accurate Due Date Calculator?
- No registration. A true accurate due date calculator no sign up required. Start calculating immediately — no accounts, no email, no spam.
- Five methods in one. Switch easily between LMP, conception, intercourse, IVF, and ultrasound. This accurate pregnancy calculator covers every scenario, including IVF due date accuracy and ultrasound due date precision.
- Cycle length adjustment. Enter your average cycle length for a personalized, more accurate due date from LMP — not just the standard 28‑day assumption.
- Complete pregnancy tracking. See your current pregnancy week, trimester, baby's size and weight, estimated conception date, and days remaining — all updated in real time.
- Birth probability calendar. Visualize your due date window with a calendar that highlights the two weeks before and after your EDD — the period when most babies are born.
- Key milestones. Track when you'll reach important pregnancy milestones — first heartbeat, end of first trimester, anatomy scan, viability, full term, and more.
- 100% private. All calculations happen in your browser. No personal health data is ever uploaded or stored.
- Works on any device. Phone, tablet, or computer — just a modern browser.
Pregnancy Timeline: Key Milestones
| Milestone | Timing | What Happens |
|---|---|---|
| First Heartbeat | Weeks 6–9 | Baby's heartbeat can be detected via transvaginal ultrasound. |
| End of First Trimester | Week 12 | Risk of miscarriage drops significantly. |
| Anatomy Scan | Weeks 18–22 | Mid‑pregnancy ultrasound checks baby's development. Parents can often learn the baby's sex. |
| Viability | Week 24 | A baby born at this stage has a chance of survival with intensive medical care. |
| End of Second Trimester | Week 28 | Third trimester begins. Prenatal visits become more frequent. |
| Full Term | Week 37 | Baby is considered full term. Lungs are mature and ready for life outside the womb. |
| Due Date | Week 40 | Only 4–5% of babies are born on their exact due date. |
Pregnancy Terms at a Glance
| Term | Weeks | What It Means |
|---|---|---|
| Preterm | Less than 37 weeks | May need extra medical support. |
| Early Term | 37 weeks – 38 weeks, 6 days | Healthy, but final development is still underway. |
| Full Term | 39 weeks – 40 weeks, 6 days | Optimal window for delivery. |
| Late Term | 41 weeks – 41 weeks, 6 days | Monitoring or induction may be discussed. |
| Post-term | 42 weeks and beyond | Labor might be induced to reduce risks. |
Step‑by‑Step: How to Use the Accurate Due Date Calculator
- Choose your calculation method. Click one of the five tabs — Last Period, Conception, Intercourse, IVF Transfer, or Ultrasound. LMP is selected by default.
- Enter your details. Fill in the required fields. For LMP, enter the first day of your last period and your average cycle length. For IVF, select the embryo age. For ultrasound, enter the gestational age from your scan report.
- Click "Calculate My Due Date". Your estimated due date appears instantly, along with your pregnancy week, trimester, baby's size and weight, conception date, days remaining, birth probability calendar, and key milestone dates.
Frequently Asked Questions
Q: How accurate is this due date calculator?
A: It uses Naegele's Rule (LMP + 280 days) adjusted for cycle length, plus standard IVF and ultrasound formulas — the same methods used in clinical practice. Only 4–5% of babies arrive exactly on the due date, but this accurate pregnancy due date calculator gives you the best estimate possible without an early ultrasound. For the highest precision, use the ultrasound method with measurements from a first‑trimester scan.
Q: Can I use this calculator if my cycles are irregular?
A: Yes. The LMP method adjusts for your average cycle length, which helps. However, for very irregular cycles, an early ultrasound provides the most accurate dating. This due date calculator for irregular periods gives you the best estimate possible with the information you have.
Q: Is this calculator free to use?
A: Yes, 100% free. No sign‑up, no registration, and no hidden costs. Calculate your due date as many times as you need — it's a truly free accurate due date calculator.
Q: Does this calculator work for IVF pregnancies?
A: Absolutely. Select the IVF Transfer method and enter the transfer date along with the embryo age (day 3 or day 5 blastocyst). The due date is calculated from the transfer date plus 263 or 261 days respectively. This accurate IVF due date calculator reflects the exact embryo age.
Q: Is my data stored or shared?
A: Never. All calculations run locally in your browser. No personal health information is ever uploaded, stored, or shared with any server or third party. Your privacy is guaranteed.
Learn how to use this tool correctly by reading our step-by-step tutorial.
