Due Date Calculator
Track your due date instantly with our free Due Date Calculator. Fast, accurate health calculations — no sign-up needed.
Estimate a pregnancy schedule from your last period, conception date, or due date.
How We Calculate Results
This calculator uses Naegele’s Rule, the standard obstetric method for estimating a due date: it adds 280 days (40 weeks) to the first day of your last menstrual period.
The result is based on the inputs you provide and the assumptions described below. Learn more about how WIN Calculator develops and reviews its calculations.
Example
For example, try re-running the calculator with a slightly different weight, height, or activity level to see how sensitive your result is to small changes in your inputs.
Assumptions
- Formulas are population-level averages developed for typical adults — they don't account for individual body composition, medical conditions, medications, or pregnancy unless the calculator is specifically designed for that case.
- Inputs are taken at face value; the calculator can't verify your measurements or correct for measurement error.
Limitations
- Formulas developed for general or athletic populations may be less accurate for children, older adults, pregnant people, or people with significant muscle mass or a diagnosed medical condition.
- This is a general estimate, not a clinical measurement — lab tests, imaging, or an in-person exam from a qualified professional will always be more accurate for anything that matters medically.
Sources
- Published formulas and reference ranges from recognized health authorities — including the CDC, WHO, NIH, and peer-reviewed clinical or exercise-science literature — see the formula above for the specific source this calculator uses.
Validation
- Every formula in our calculator library is covered by an automated regression test suite that checks its output against known reference values before any code change ships.
- Formulas are written from publicly documented sources — standards bodies, government agencies, or established textbooks — rather than derived from scratch, and are reviewed again whenever the underlying guidance changes.
Health Disclaimer
This calculator is for general informational and educational purposes only. It does not diagnose, treat, or provide a clinical assessment of any health condition, and it is not a substitute for advice from a qualified healthcare provider. Always talk to a doctor or other qualified professional about your personal health.
About the Due Date Calculator
The Due Date Calculator is a free online tool built for everyday health and fitness tracking, so you can monitor progress without guesswork. Track your due date instantly with our free Due Date Calculator. Fast, accurate health calculations — no sign-up needed. It’s part of our Fitness & Health calculator collection — bmi, calories, body fat, pregnancy, and more.
Results are calculated instantly in your browser using standard, widely accepted formulas for this type of calculation, and are intended for general estimation and educational purposes rather than as a substitute for professional financial, medical, or legal advice.
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