Birth Date Probability Calculator
The real arrival-date distribution around your EDD — week-by-week odds instead of one misleading date.
Median first pregnancies run ~2–3 days past the EDD, and the spread is wide by nature: ±2 weeks captures ~90% of spontaneous births. The single-date EDD is a planning convention from 1812; the distribution is the truth. Induction policies (commonly offered at 41 weeks) cut the right tail in practice.
Formula
For general information only. Pregnancy and infant care decisions must be guided by your treating clinician or midwife — always defer to their assessment.
Disclaimer: This tool is for general informational and estimation purposes only and is not professional financial, tax, accounting or legal advice. All figures are estimates — verify with a qualified professional before making decisions. Read the full disclaimer.
The real arrival-date distribution around your EDD — week-by-week odds instead of one misleading date. The Birth Date Probability Calculator is a free, private chance of birth by date tool — every result computes instantly in your browser with no sign-up and no data upload.
About Birth Date Probability Calculator
Median first pregnancies run ~2–3 days past the EDD, and the spread is wide by nature: ±2 weeks captures ~90% of spontaneous births. It applies distribution from prospective cohorts (Jukic 2013; Smith 2001). Use the Birth Date Probability Calculator to get an instant, clearly-explained result with the working shown step by step — free, private and with the source method cited.
How to use Birth Date Probability Calculator
- 1Enter your details in the Birth Date Probability Calculator input fields above.
- 2The result updates instantly with the working and reference bands shown.
- 3Adjust any value to explore how it changes the outcome — it's free and unlimited.
Why use Birth Date Probability Calculator?
- ✓Instant chance of birth by date result that recomputes as you type — no waiting, no page reloads
- ✓100% client-side: your health data never leaves your browser
- ✓Shows the actual formula and your numbers substituted in, so you can see exactly how the result is reached
- ✓Based on published, citable sources (Jukic AM et al., Hum Reprod 2013)
- ✓Free forever with no sign-up, account or app install
Frequently asked questions
How does the Birth Date Probability Calculator work?+
Median first pregnancies run ~2–3 days past the EDD, and the spread is wide by nature: ±2 weeks captures ~90% of spontaneous births. The calculation uses the formula: distribution from prospective cohorts (Jukic 2013; Smith 2001). Everything runs instantly in your browser as you type — your inputs are never uploaded.
Is the Birth Date Probability Calculator accurate, and what is it based on?+
The method is traceable to authoritative sources, including Jukic AM et al., Hum Reprod 2013; Smith GCS, Hum Reprod 2001 — gestational length cohort. Results are estimates — individual variation always applies, so treat the output as a well-grounded starting point.
Is the Birth Date Probability Calculator free and private?+
Yes. It's completely free with no sign-up, and all computation happens locally in your browser, so none of your health data ever leaves your device.
Can I use this for medical decisions?+
This tool is informational only. Always defer to your treating clinician or midwife for pregnancy and infant care decisions.
What can I use the Birth Date Probability Calculator for?+
It's commonly used for chance of birth by date, due date probability, when will baby arrive. The real arrival-date distribution around your EDD — week-by-week odds instead of one misleading date.
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