Pregnancy Due Date Calculator
Pregnancy due date calculator estimates your expected delivery date from LMP, conception, ultrasound, or IVF transfer. Find your current week and trimester in seconds.
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Formula
The calculator supports multiple method paths and estimates weeks remaining and trimester.
Worked Example
How Pregnancy Due Dates Are Estimated
- LMP method: add 280 days to the first day of your last menstrual period. This is the standard obstetric dating method
- Conception method: add 266 days (38 weeks) from the known or estimated date of conception
- Ultrasound method: the most accurate early in pregnancy, especially when done before 12 weeks
- IVF method: add 266 days minus embryo age at transfer for the most precise calculation in IVF pregnancies
Only about 5% of babies are born on their exact due date. Most arrive within 2 weeks before or after. Always consult your healthcare provider for personalized guidance.
You can also calculate changes using our Ovulation Calculator, IVF Calculator or Gestational Age Calculator.
Frequently Asked Questions
Is this a medical diagnosis?
No. This is a planning estimate. Due dates are approximations, and only about 5% of babies arrive on the exact predicted date. Consult your healthcare provider for medical guidance.
Which method is most accurate?
First-trimester ultrasound dating is generally the most accurate. The LMP method is the standard starting point but can be off if cycles are irregular or the exact LMP date is uncertain.
Can my due date change?
Yes. Your healthcare provider may adjust your due date based on ultrasound measurements, especially if there is a significant difference from the LMP-based estimate.
What is the IVF transfer method?
For IVF pregnancies, the due date is calculated from the known transfer date minus the embryo age at transfer. A day-5 blastocyst transfer adds 261 days, and a day-3 embryo transfer adds 263 days. This is the most precise method because both dates are medically documented.
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. It assumes a 28-day cycle with ovulation on day 14. Your provider may adjust for longer or shorter cycles. This calculator is for planning purposes only and is not a substitute for medical advice.
How are pregnancy trimesters divided?
The first trimester spans weeks 1 to 12, the second trimester covers weeks 13 to 27, and the third trimester runs from week 28 to 40. Each phase has distinct developmental milestones. Consult your healthcare provider for personalized prenatal care guidance.
Medical Disclaimer
This calculator is provided for informational and educational purposes only. It is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before making any decisions based on these results. Do not disregard or delay seeking medical advice because of information obtained from this tool.
AI Assistant
Ask about this calculator
I can help you understand the pregnancy due date calculator formula, interpret your results, and answer follow-up questions.
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Our AI assistant provides general estimates and advice only. Please consult a qualified healthcare professional before making any health-related decisions.
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