Pregnancy Weeks and Trimester Calculator
Enter how far along you are to see your trimester and time remaining.
Your numbers
Your results
Pregnancy Weeks and Trimester Calculator by TheCalcTools
How the Pregnancy Weeks and Trimester Calculator works
Enter the gestational age your care provider gave you, in completed weeks and days.
Trimesters are counted from the first day of the last menstrual period.
A full-term pregnancy is about 40 weeks (280 days).
The formula
Worked example
Using the default values shown in the calculator:
| Weeks | 20 |
|---|---|
| Days | 3 |
- 20 weeks 3 days is 20 × 7 + 3 = 143 days.
- You are in the Second (14 to 27 weeks 6 days) trimester.
- There are 19 weeks 4 days to go, and you are 51.1% of the way through.
Result:
| Days pregnant | 143 |
|---|---|
| Trimester | Second (14 to 27 weeks 6 days) |
| Days to 40 weeks | 137 |
| Weeks and days to 40 weeks | 19 weeks 4 days |
| Complete (of 40 weeks) | 51.1% |
Frequently asked questions
How is gestational age counted?
From the first day of the last menstrual period, which is about two weeks before conception, so a 40-week pregnancy is around 38 weeks from conception.
Is 40 weeks a deadline?
No. Only a minority of babies arrive exactly on the due date. Term is considered 37 to 42 weeks.
Sources and further reading
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This calculator gives general estimates for information and education. It is not medical advice and does not diagnose anything. Talk to a qualified health professional about your own situation. See our disclaimer.