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Pregnancy Calculator
About the Pregnancy Calculator
Work out how far along you are, your due date and key milestones. Choose whether to calculate from your last period, the date of conception, or a due date you already know.
How to use the Pregnancy Calculator
- Pick a Calculation Method: First Day of Last Period (LMP), Exact Date of Conception or Already Know My Due Date.
- Enter the Date that matches your method and your Average Cycle Length (Days).
- Press Generate Report to see your due date, weeks and days pregnant, trimester and important milestones.
Formula and method
Pregnancy is counted as 40 weeks from the first day of the last period, which is about 38 weeks from conception. Trimesters: first up to 13 weeks, second 14 to 27 weeks, third 28 weeks to birth.
Worked example
With an LMP of 1 January and a 28-day cycle, on 12 March you are 10 weeks and 0 days pregnant, in the first trimester.
Tips
- Your midwife or doctor will confirm dates with an ultrasound scan.
- Book antenatal appointments early and take folic acid as advised by your doctor.
Frequently Asked Questions
Weeks are counted from the first day of the last period because the exact moment of conception is usually not known.
At 14 weeks of pregnancy.