This pregnancy due date calculator estimates a due date from dating inputs such as last menstrual period style calculations used in educational tools. Clinical dating may differ. This is not medical advice and does not replace prenatal care.
Estimated due dates help with planning, but only a clinician can interpret ultrasound dating and individual medical context. This due date calculator is an educational Naegele style estimate, not prenatal care and not a diagnosis.
Related: conception calculator and pregnancy tools under pregnancy. Full list in the calculators archive.
What LMP dating assumes
The common 280 day estimate assumes a 28 day cycle with ovulation around day 14. Cycles vary. Irregular periods, recent birth control changes, and breastfeeding can shift ovulation. Ultrasound dating may revise the estimate.
How to estimate a pregnancy due date
- Enter the first day of the last menstrual period.
- Calculate to see the estimated due date.
- Read the approximate week count from LMP to today when shown.
- Confirm dates with your healthcare provider.
How the calculation works
Due date = LMP date + 280 days
Week count uses elapsed time from LMP to today in whole weeks. Day count from LMP is also available in the detail output. This matches Multicalify due date logic.
Example: LMP on 1 January 2026 yields a due date near 8 October 2026 after 280 days, subject to calendar display formatting.
Due date versus conception estimates
Conception timing tools estimate when fertilization may have occurred. Due date tools estimate delivery timing from LMP. Use each page for its intent so results stay clear.
Due date mistakes with irregular cycles
- Entering the end of the period instead of the first day
- Assuming every cycle is 28 days
- Ignoring clinician ultrasound revisions
- Using the estimate in place of prenatal appointments
Limitations and care guidance
Only a fraction of births occur on the exact EDD. Contact a qualified clinician for prenatal care, screening schedules, and urgent symptoms. Multicalify does not provide medical services.
Using due date estimates alongside clinical care
Estimate a date for personal planning, then defer to clinical dating for medical decisions. Ask your clinician how they set and update your official due date.
Why providers may change the date
Early ultrasound measurements can be more reliable than LMP when cycles are uncertain. Providers may reconcile LMP and ultrasound using clinical protocols. If your app date and clinic date differ, follow the clinic record for appointments and testing windows.
Track symptoms and questions for visits rather than refreshing calculators repeatedly. The educational estimate is most useful once, then confirmed medically.
LMP dating versus ultrasound revisions
Clinicians may revise dates based on ultrasound. A calculator locked to one input will not track those revisions automatically. Follow your care team’s dating for appointments and testing schedules.
If you also explore conception timing, keep assumptions consistent between tools and treat both as estimates.
Related: Conception Calculator.