Due Date Calculator
Estimate from the first day of the last menstrual period
Quick guide
What can Due Date Calculator help you do?
Estimate a pregnancy due date from the first day of the last menstrual period using the conventional 280-day method for a regular 28-day cycle.
Best for
Turn the first day of a last menstrual period into a preliminary due-date entry for your notes. This is a single-date calculator: it has no conception-date, embryo-transfer, or examination-results mode, and cannot adjust the calculation for an individual cycle length.
How to use it
Replace the date, initially today, with the first day of the last menstrual period, not its final day. Results update when you edit or click Calculate. Future dates are rejected. Reset restores the default date established when this page was opened.
How to read the result
The displayed date is exactly 280 calendar days after your input, formatted for the selected language. The model assumes a regular 28-day cycle. It supplies one estimated date, without gestational age, an uncertainty interval, or a prediction of the actual delivery date.
Privacy and limits
The component adds days in your browser; it does not submit the menstrual date to a due-date API or provide saved records. The page still loads site analytics and potentially other external resources. Be mindful of visible dates when sharing screenshots or using a shared screen.
This is a date-formula estimate, not pregnancy confirmation, clinical dating, or medical advice. The program does not assess whether an old input date fits your present circumstances, and it does not model irregular cycles. A calculated date cannot replace an individual medical assessment.
Frequently Asked Questions
Is this tool free?
Yes. It runs in your browser and does not require sign-in.
Is the result exact?
The result is a practical estimate or conversion. For tax, medical, legal, or financial decisions, verify with a qualified source.