👶 Due Date Calculator
Calculate your pregnancy due date using LMP (Naegele's Rule), conception date, IVF transfer date, or ultrasound. Get your estimated due date, current gestational age, trimester breakdown, and a milestone timeline.
What Is a Due Date Calculator?
A due date calculator estimates when your baby is likely to be born. It uses standard obstetric formulas based on your last menstrual period (LMP), conception date, IVF transfer date, or ultrasound measurements.
The estimated due date (EDD) is calculated as 40 weeks (280 days) from the first day of your last menstrual period, following Naegele's Rule. If you know your conception date, the EDD is 38 weeks (266 days) from that date .
How Does the Due Date Calculator Work?
This calculator supports four methods:
- Last Menstrual Period (LMP): EDD = LMP + 280 days (adjusted for cycle length). The most common method used by healthcare providers.
- Conception Date: EDD = Conception date + 266 days. Best if you know your ovulation date or used ovulation testing.
- IVF Transfer Date: EDD = Transfer date + 266 − embryo age. For a Day 5 blastocyst transfer, EDD = Transfer date + 261 days.
- Ultrasound: EDD = Scan date + (280 − gestational age at scan in days). First-trimester ultrasound (CRL measurement) is the gold standard.
The calculator also shows your current gestational age, trimester, progress bar, and a milestone timeline with key prenatal checkpoints.
Why Use This Due Date Calculator?
- Four calculation methods: LMP, conception, IVF, and ultrasound.
- Cycle length adjustment: Adjusts for cycles longer or shorter than 28 days.
- Gestational age: Shows how far along you are in weeks and days.
- Trimester breakdown: Identifies which trimester you are in.
- Progress bar: Visual representation of pregnancy progression.
- Milestone timeline: Key dates for screenings, tests, and checkpoints.
- Free & private: No registration, no data storage , all calculations are done in your browser.
❓ Due Date Calculator FAQ
What is Naegele's Rule?
Naegele's Rule estimates the due date by adding 280 days (40 weeks) to the first day of your last menstrual period. Alternatively, add 7 days and subtract 3 months from your LMP.
How accurate is the due date?
Only about 4% of babies are born on their exact due date. Most babies arrive between 38 and 42 weeks. Due dates are estimates, not deadlines.
Which method is the most accurate?
An early ultrasound (first trimester, 7–13 weeks) is the gold standard, with an accuracy of ±5–7 days. Later ultrasounds (second/third trimester) are less accurate for dating.
What if my cycle is longer or shorter than 28 days?
The LMP method assumes a 28-day cycle with ovulation on day 14. For longer cycles, add the difference: a 30-day cycle adds 2 days, a 35-day cycle adds 7 days. The calculator automatically adjusts for your cycle length.
How is the IVF due date calculated?
For IVF, the due date is calculated from the oocyte retrieval date + 266 days. If using the transfer date, subtract the embryo age (e.g., 3 or 5 days). A Day 5 transfer → EDD = Transfer date + 261 days.
What is gestational age?
Gestational age is the time elapsed since the first day of your last menstrual period, measured in weeks and days. It is about 2 weeks longer than the baby's actual fetal age (time since conception).
What are the trimesters?
First trimester: Weeks 1–13. Second trimester: Weeks 14–27. Third trimester: Weeks 28–40. Each trimester has distinct developmental milestones and prenatal care schedules.
Can my due date change?
Yes. If an early ultrasound shows a significant discrepancy from your LMP-based date (more than 5–7 days), your healthcare provider may adjust the due date based on the ultrasound.
How accurate is this calculator?
This calculator uses standard obstetric formulas (Naegele's Rule, ACOG guidelines). Accuracy depends on the input method. LMP-based dates are less accurate for irregular cycles; ultrasound-based dates are more reliable. Always confirm with your healthcare provider.
Is this calculator free?
Yes, this calculator is completely free to use. No registration or personal data storage is required.