About this due date calculator
This tool estimates a pregnancy due date from either the first day of your last menstrual period (LMP) or a known conception date. It is meant to help you understand the common calculation, not to confirm a pregnancy timeline clinically.
Source and review information
- Last updated
- 2026-04-26
- Last reviewed
- 2026-04-26
- Created by
- nibcat editorial team
- Medical review
- Not medically reviewed
This tool is based on publicly available guidance from health authorities and professional organizations. It is for general information only and does not provide medical diagnosis, treatment, pregnancy management, or clinical advice.
Important medical note
A due date is an estimate. The actual birth date is commonly before or after the estimated date, and a clinician may adjust the date based on menstrual history, cycle length, ovulation or conception timing, early ultrasound findings, and other clinical information. If you have bleeding, severe abdominal pain, feel unwell, or need an individual decision about pregnancy care, contact a doctor, midwife, or local healthcare service.
How the estimate is calculated
The calculator keeps the calculation narrow: it estimates dates only. Healthcare providers may confirm or adjust an estimated due date using first-trimester ultrasound and clinical history.
Due date (LMP) = LMP + 280 days + (cycle length - 28) Due date (conception) = Conception date + 266 days Gestational age = (Today - LMP) / 7
Why your clinician may adjust the date
Cycle length, uncertain ovulation timing, uncertain conception timing, and early ultrasound measurements can change the estimated due date. If a healthcare professional has already given you a due date, use that date for appointments, records, and care planning.
Privacy note for share links
A copied share link can include the date you entered. Because that may reveal pregnancy-related personal information, share it only with people you trust.
Official resources
For food, nutrition, supplements, medicines, appointments, and pregnancy care decisions, use official public-health information and your own healthcare team. Guidance can differ by country and personal circumstances.
Frequently asked questions
Is this due date exact?
No. It is an estimate. Many babies are born before or after the estimated date, and clinical information can change the estimate.
Why is my clinician's due date different?
A clinician may use cycle history, a known conception date, early ultrasound, and other clinical information. Use your clinician's date for care planning.
Should I use LMP or conception date?
Use the date you know most reliably. LMP is the usual starting point for gestational age; a known conception date can also estimate the due date.
Does this replace medical advice?
No. It does not provide diagnosis, treatment, clinical advice, or pregnancy management. Ask a qualified healthcare professional for individual concerns.
Does the share link include my input?
Yes. The link can include the entered date, so share it only with people you trust.