Due Date Calculator
Enter your last menstrual period, conception date, or IVF transfer date to estimate when your baby will arrive.
📅 Last Period (LMP)
🔬 Conception Date
🩺 IVF Transfer Date
Select the first day of your most recent menstrual period
Most cycles are 28 days. Adjust if yours differs.
How Is My Due Date Calculated?
We use Naegel’s Rule, the same method your OB/GYN uses. Starting from the first day of your last menstrual period (LMP), we add 280 days (40 weeks). If your cycle is longer or shorter than 28 days, we adjust accordingly.
Keep in mind: Only about 5% of babies are born on their actual due date. Most arrive within a 2-week window around the estimated date. Your due date may be adjusted after an early ultrasound measurement.
Frequently Asked Questions
How accurate is a due date calculator? +
Due date calculators provide an estimate within ±2 weeks. First-trimester ultrasounds (7–11 weeks) are the most accurate dating method, typically within ±5 days. Your provider may adjust your due date based on ultrasound measurements.
What if I don’t know my last period date? +
If you’re unsure of your LMP, your healthcare provider can estimate your due date using an early ultrasound measurement (crown-rump length). You can also use the “Conception Date” or “IVF Transfer Date” tabs above if those dates are known.
Can my due date change? +
Yes. Your doctor may adjust your due date after your first ultrasound if the baby’s measurements don’t match your LMP-based date. A difference of more than 7 days in the first trimester typically warrants a revision.
How does IVF due date calculation work? +
For IVF, the due date is calculated backward from the transfer date. A day 5 blastocyst transfer adds 261 days; a day 3 embryo transfer adds 263 days. This accounts for the embryo’s age and the standard 14-day gap between LMP and ovulation.
What’s the difference between gestational age and fetal age? +
Gestational age (what OBs use) is counted from the first day of your LMP — typically 2 weeks before conception. Fetal age (actual embryo age) is 2 weeks less. All due date calculations use gestational age by convention.
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⚕️ Medical Disclaimer: This tool provides an estimate only and does not constitute medical advice. Due date calculations are most accurate when confirmed by your healthcare provider through ultrasound dating.