What a due date estimate means
A due date is an estimate, not a guarantee. Many pregnancies do not deliver on the exact estimated date. Clinical dating may change after ultrasound, cycle history, embryo transfer details, or prenatal assessment.
How this calculator works
For last menstrual period, the calculator adds about 280 days and adjusts for cycle length. For conception date, it adds about 266 days. For IVF, it adjusts based on embryo age at transfer.
When to rely on professional dating
Use prenatal care for medical decisions. If dates conflict, if cycles are irregular, or if there are concerns about pregnancy progress, a clinician can interpret ultrasound and medical history. This calculator does not provide prenatal care or emergency guidance.
Quick interpretation table
| LMP method | Common estimate based on last menstrual period plus cycle adjustment. |
| Conception method | Uses estimated conception date plus about 266 days. |
| IVF method | Uses transfer date and embryo age. |
| Trimester display | Calculated from estimated gestational age. |
Example result
If the last menstrual period began on January 1 with a 28-day cycle, the estimated due date is roughly 280 days later. If the average cycle is longer, the estimate shifts later; if shorter, it shifts earlier.