Pregnancy milestones: weeks, trimesters and key dates
Enter the first day of your last period (or the due date from your care team). The tool places the pregnancy at the chosen date, or today if you leave that box empty.
General information, not medical advice. This result does not replace a doctor. If in doubt or if you have symptoms, see a health professional.
Result
23 weeks + 1 daysGestational age (from the last period)
- Trimester
- 2
- Days until the estimated due date
- 118
- Second trimester starts (14 weeks)
- August 7, 2026
- Third trimester starts (28 weeks)
- November 13, 2026
- Estimated due date (40 weeks)
- February 5, 2027
- An indication only: the dating used by your care team (often the first-trimester scan) always comes first.
Inputs
- I know
- The first day of my last period
- Date
- 2026-05-01
- Usual cycle length
- 28
- On the date
- 2026-10-10
How it is calculated
Gestational weeks are counted from the first day of the last period.
Result
Gestational age (from the last period)
- Trimester
- 2
- Days until the estimated due date
- 118
- Second trimester starts (14 weeks)
- August 7, 2026
How it is calculated
- Gestational weeks are counted from the first day of the last period.
- For a cycle other than 28 days, the start moves by (cycle − 28) days. From a known due date, the start is the due date − 280 days.
- Trimesters: first before 14 weeks, second 14 to 27 weeks, third from 28 weeks. Estimated due date: 40 weeks.
Example
Period on 1 May 2026, 28-day cycle, on 10 October 2026: 23 weeks + 1 day, second trimester; estimated due date 5 February 2027, in 118 days.
Good to know
- Does not replace medical dating: a first-trimester scan is more accurate than period dates.
- Trimester boundaries vary slightly between countries and sources.
- For any question about your pregnancy, ask your midwife or doctor.
Sources
- ACOG Committee Opinion 700, Methods for estimating the due date, 2017
- NICE guideline NG201, Antenatal care, 2021
Frequently asked questions
What is this tool used for?
Enter the first day of your last period (or the due date from your care team). The tool places the pregnancy at the chosen date, or today if you leave that box empty.
How is the result calculated?
Gestational weeks are counted from the first day of the last period.
What should I check before using the result?
Does not replace medical dating: a first-trimester scan is more accurate than period dates.