Due Date Calculator
Estimate your baby's due date and pregnancy milestones.
Due dates are estimates and do not replace prenatal medical care.
Due date calculator
Choose a calculation method and enter the date details you know.
LMP method assumes ovulation around day 14 of a 28-day cycle.
Cycle length can shift estimated ovulation and due date. Accepted range: 21–45 days; leaving it blank uses 28 days.
Due dates are estimates. Pregnancy care should be guided by qualified healthcare professionals, and ultrasound dating or clinician assessment may revise the date.
Pregnancy timeline overview
Calculation methods explained
Last menstrual period
Uses the first day of your last menstrual period plus cycle-length adjustment.
Conception date
Uses a known or estimated conception date.
IVF transfer
Uses embryo transfer date and embryo age.
LMP vs conception date vs ultrasound dating
LMP is common because many people know their last period date. Conception date can be harder to know exactly.
Ultrasound dating may be used clinically, especially early in pregnancy. Irregular cycles can make LMP-based estimates less accurate.
Trimester guide
First trimester
Weeks 1–13
Early pregnancy is commonly counted from the first day of the last menstrual period.
Second trimester
Weeks 14–27
Many people have anatomy scans and ongoing prenatal visits during this stage.
Third trimester
Weeks 28–40+
The final trimester includes continued growth, monitoring, and birth preparation.
Week boundaries can vary slightly by source. Prenatal care schedules should come from a clinician.
Why due dates can change
Exact delivery date cannot be predicted by a calculator. A due date is a planning estimate, not a deadline.
Limitations and medical disclaimer
Calculator results are informational only. Dates are estimates, and pregnancy care should be guided by healthcare professionals.
IVF details and complex medical histories should be reviewed clinically.
Seek urgent medical attention for symptoms such as heavy bleeding, severe abdominal pain, fainting, severe headache, chest pain, shortness of breath, or reduced fetal movement later in pregnancy.
Formula / date explanation
LMP method: Estimated Due Date = First Day of Last Menstrual Period + 280 days + (cycle length − 28 days)Conception method: Estimated Due Date = Conception Date + 266 daysIVF method: Estimated Due Date = Transfer Date + 266 days − embryo age (5-day: + 261 days; 3-day: + 263 days)280 days is about 40 weeks from LMP. With a 28-day cycle the cycle adjustment is 0 days; a 35-day cycle adds 7 days and a 21-day cycle subtracts 7 days. 266 days is about 38 weeks from conception. IVF due date depends on transfer date and embryo age. Ultrasound or clinician assessment may override calculator estimates.
Sources: ACOG: Methods for Estimating the Due Date and NHS: Pregnancy due date calculator.
Frequently Asked Questions
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Estimate only. This calculator is for general education and planning. It is not medical advice, and not medical, nutrition, fitness, diagnosis, treatment, or emergency advice. Personal factors can change results. Dates are estimates based on the inputs provided. Cycle length, ovulation timing, pregnancy dating, and medical factors can vary. Speak with a qualified professional for personal guidance.
Related reading
Learn the formula, assumptions, examples, or context behind this tool.