Pregnancy Calculator
Track pregnancy week by week with trimester dates and key milestones.
Inputs
Used to compute current gestational age.
Weeks pregnant
25
Days into current week
6
Current trimester
2
Estimated due date
2025-10-08
Days until due date
99
Progress
65%
1st trimester starts
January 1, 2025
2nd trimester starts
April 2, 2025
3rd trimester starts
July 9, 2025
Step by step
LMP
= January 1, 2025
Days since LMP
= 181
Gestational age
= 25 weeks + 6 days
Trimester
= 2
Due date (Naegele's rule)
= October 8, 2025
Days until due date
= 99
Key milestones
| Week | Milestone | Date |
|---|---|---|
| 6.00 | Heartbeat detectable (ultrasound) | 2025-02-12 |
| 13.00 | End of 1st trimester | 2025-04-02 |
| 20.00 | Anatomy scan | 2025-05-21 |
| 27.00 | End of 2nd trimester | 2025-07-09 |
| 28.00 | Glucose tolerance test | 2025-07-16 |
| 24.00 | Viability threshold | 2025-06-18 |
| 39.00 | Full term begins | 2025-10-01 |
| 40.00 | Due date (40 weeks) | 2025-10-08 |
How it works
Gestational age is measured from the first day of the last menstrual period (LMP), not from conception, because LMP is more reliably known. A full-term pregnancy is 40 weeks (280 days) from LMP. The trimesters are weeks 1–12, 13–26 and 27–40. The due date from LMP is calculated using Naegele's rule: add 1 year, subtract 3 months, add 7 days.
Formula
Naegele's rule
EDD = LMP + 1 year − 3 months + 7 days (≡ LMP + 280 days)
- EDD
- Estimated due date
- LMP
- First day of last menstrual period
This calculator is for informational and educational purposes only. It is not a substitute for prenatal care or advice from a qualified healthcare provider. Always confirm gestational age with your obstetrician or midwife.
Frequently Asked Questions
Why is pregnancy counted from the last period, not conception?
The exact date of conception is usually unknown, whereas the start of the last period is a concrete, remembered date. Gestational age dating from LMP is universal in clinical practice and in this calculator.
When do the trimesters start and end?
First trimester: weeks 1–12 (conception through 12 weeks). Second trimester: weeks 13–26. Third trimester: weeks 27–40. These boundaries vary slightly by source; this calculator uses the most common clinical division.
How accurate is the due date?
Only about 5 % of babies are born exactly on their due date. Most births occur within 2 weeks before or after. An early ultrasound (before 13 weeks) is more accurate than LMP dating when cycles are irregular.