Why people use pregnancy calculators
Pregnancy is tracked in weeks, but life is organised in dates. Converting between the two — due date, current week, trimester boundaries, days remaining — is something expectant parents do constantly when booking appointments, planning leave and preparing at home.
How these calculators work
Standard dating counts forty weeks from the first day of the last menstrual period, which is the method used here. From that anchor the calculator derives the estimated due date, the current gestational week and the time remaining.
An estimated due date is exactly that: only a small minority of babies arrive on it, and a dating scan may shift the estimate. This tool is for information and planning and is not a substitute for advice from a midwife or doctor.
Tips
- If a scan has given you a revised due date, work back forty weeks and use that date as your input.
- Trimester boundaries are conventionally set at weeks 13 and 27.
- The related pregnancy calculators below cover due dates, weeks and countdowns from the same information.