Use this pregnancy months calculator to estimate how many weeks and months pregnant you are, your trimester, and your estimated due date based on the first day of your last menstrual period (LMP).
How to use this pregnant months calculator
Pregnancy is usually tracked in weeks, but many people naturally ask, “How many months pregnant am I?” This tool helps you convert your timeline into both formats so it is easier to understand and share.
- Enter the first day of your LMP.
- Optionally set a custom as of date to check your pregnancy status for a specific day.
- Adjust your cycle length if your cycle is regularly shorter or longer than 28 days.
- Click calculate to get your weeks pregnant, pregnancy month, trimester, and estimated due date.
Why weeks and months can look different
Pregnancy dating can be confusing because calendar months are not all exactly 4 weeks long. Medical providers usually use gestational age in weeks because it is more precise for prenatal milestones, ultrasounds, and appointment planning.
For example, someone who is 20 weeks pregnant might say they are around 4.5 to 5 months pregnant, depending on the month mapping method. That is normal. This calculator shows both perspectives to reduce confusion.
Standard pregnancy month chart (clinical approximation)
| Pregnancy Month | Gestational Weeks | Trimester |
|---|---|---|
| Month 1 | Weeks 1-4 | First Trimester |
| Month 2 | Weeks 5-8 | First Trimester |
| Month 3 | Weeks 9-13 | First Trimester |
| Month 4 | Weeks 14-17 | Second Trimester |
| Month 5 | Weeks 18-22 | Second Trimester |
| Month 6 | Weeks 23-27 | Second Trimester |
| Month 7 | Weeks 28-31 | Third Trimester |
| Month 8 | Weeks 32-35 | Third Trimester |
| Month 9 | Weeks 36-40+ | Third Trimester |
What your results mean
1) Gestational age (weeks + days)
This is the most important number for pregnancy care. It is counted from your LMP, not from the day of conception.
2) Pregnancy month
This is an approximate conversion from weeks into month ranges. It is helpful for everyday conversation.
3) Trimester
- First trimester: up to 13 weeks
- Second trimester: 14 to 27 weeks
- Third trimester: 28 weeks onward
4) Estimated due date (EDD)
The estimated due date is typically calculated as 280 days (40 weeks) from LMP, with optional cycle-length adjustment. It is an estimate, not a guarantee. Many healthy pregnancies deliver before or after this date.
Frequently asked questions
How accurate is a pregnancy months calculator?
It is generally accurate for timeline estimation, especially if your LMP is known and your cycle is regular. Clinical dating may be updated using early ultrasound findings.
Can I calculate from conception date instead?
Most medical systems use LMP because conception day is often uncertain. If conception is known, gestational age is often estimated by adding about 14 days to conception timing.
Why does my app show a different month than another tool?
Different apps use different month boundaries. Week-based gestational age is the consistent clinical standard.
What if my cycle is longer than 28 days?
A longer cycle can shift ovulation later, which may slightly shift estimated due date. That is why this calculator includes cycle-length input for due date adjustment.
Bottom line
Use this pregnant months calculator when you want a clear snapshot of your pregnancy timeline: weeks pregnant, months pregnant, trimester, and due date in one place. It is ideal for planning appointments, understanding milestones, and tracking progress in a practical way.