Pregnancy & beyond
Due date calculator
A due date is an estimate that helps organise pregnancy care. It cannot predict the day a baby will be born, confirm a pregnancy or replace the date established by your own care team.
What the date means
Menstrual-date calculators start with the first day of the last menstrual period, not the last day and not a presumed conception date. The estimate depends on the assumptions used. The NHS notes that an antenatal dating scan can give a more accurate estimate of gestational age.
How this simple tool works
The tool below uses 280 days from the first day of the last period, adjusted by the difference between the reported regular cycle length and 28 days. It is a calendar estimate. It does not identify ovulation, assess pregnancy development or establish whether a pregnancy is progressing normally.
When not to use it
Do not use this calculation for an IVF pregnancy, irregular cycles or uncertain menstrual dates. Tell your care team what information you know rather than entering a guessed date. After assisted reproduction, the team may use treatment and embryo information to establish dating.
What to do with an estimate
Bring the relevant dates to antenatal care and ask which estimated date is being used. If different records show different dates, ask the team to clarify the plan rather than choosing the date you prefer. Care decisions need the complete clinical context.
Your privacy
The calculation runs only after you press the button. The date is not submitted to the site, saved in browser storage or used to build a profile by this tool. Use Clear to remove the entries. This statement describes the calculator itself, not every technical function of the website or browser.
A useful next conversation
Ask when your first pregnancy-care appointment should take place, how dating will be confirmed and whom to contact about symptoms. An estimate should help organise a conversation, not create reassurance about a concern that needs professional assessment.
An estimated date, not a prediction
For a known last menstrual period and a regular cycle only. Not for IVF, uncertain dates or irregular cycles. Your care team’s dating takes priority.
No information is sent or stored by this calculator.
This optional calculator needs JavaScript. You can still read the complete guide without it.
Questions people ask
Is the result an exact birthday?
No. It is a calendar estimate, and the actual birth date can differ.
Can it check whether I am pregnant?
No. It cannot diagnose pregnancy or assess its health, location or viability.