Estimate a pregnancy due date and current week.
Free to use, no sign-up required. Due Date Calculator is one of 198 tools built into Xenition, alongside a chat that can use them for you.
Estimates a pregnancy due date from the first day of the last menstrual period, and shows the current week, trimester and days to go. The date is an estimate, not medical advice; an early ultrasound gives a more reliable date.
The due date is the period start plus 280 days (40 weeks), the same result as Naegele’s rule of adding a year, subtracting three months and adding seven days. Weeks are counted from the period start. The trimesters change at 13 and 27 weeks. Dates in the future or more than 45 weeks back are rejected.
A last period starting 10 January 2026 gives a due date of 17 October 2026. On 1 April 2026, 81 days later, the current week is 11w 4d, in the first trimester.
The period date is usually known and conception is not. Ovulation typically happens about two weeks later, so gestational age runs about two weeks ahead of the baby’s actual age.
Only about 4 to 5%. Most births happen within two weeks either side, and a longer or irregular cycle shifts the real date.
You do not have to open Due Date Calculator to use it. Ask Xenition in plain language and it runs the right tool, then carries the answer into whatever you are working on — a document, a spreadsheet, a deck.