Pregnancy Tools
Pregnancy Week Calculator — How Many Weeks Pregnant
Calculate current pregnancy week and trimester from last menstrual period (LMP) or due date. Educational — confirm with ultrasound dating.
Pregnancy Week Calculator on FYN Tools is a free Pregnancy Tools utility. Open Pregnancy Week Calculator in your browser — no signup required. Pregnancy Week Calculator: Maps LMP or a given date to gestational week and trimester. Input: LMP or current gestational info. Output: Week number + trimester label. Related: Pregnancy Due Date Calculator.
Privacy & processing: Calendar-based estimate only. Clinical dating may differ — follow your prenatal provider.
TL;DR: Pregnancy Week Calculator: Maps LMP or a given date to gestational week and trimester. Input: LMP or current gestational info. Output: Week number + trimester label.
Reviewed by FYN Tools Editorial · Guides ·
Data input / output
| Inputs | LMP date or due date |
|---|---|
| Outputs | Gestational week, trimester, estimated due date |
| Formats | Calendar dates |
| Limits | Not a substitute for ultrasound or clinical assessment |
| Processing | Client-side (browser) |
How to Use the Pregnancy Week Calculator
- Enter the first day of your last menstrual period (LMP).
- Review gestational week and trimester.
- Compare with ultrasound at prenatal visits.
What is a Pregnancy Week Calculator?
Pregnancy Week Calculator: Maps LMP or a given date to gestational week and trimester.
Inputs: LMP or current gestational info. Outputs: Week number + trimester label. Mistake to avoid: mixing embryonic age with gestational age (gestational is ~2 weeks ahead).
Pregnancy Week Calculator: Maps LMP or a given date to gestational week and trimester.
How it works
You set lmp or current gestational info in the live panel. Pregnancy Week Calculator then maps LMP or a given date to gestational week and trimester. Results show as week number + trimester label.
Explore more tools on our site.
Usage scenarios
- How many weeks: Enter LMP and read week + trimester.
- Appointment talk: Use the same week your clinic uses if they gave you one.
- App mismatch: If this disagrees with your prenatal app, ask the clinic which dating they use.
Input / Output Examples
Input
LMP: 1 Jan 2026
Output
Gestational week + trimester (educational)
Input
Update after ultrasound dating
Output
Revised week count for appointments
Frequently Asked Questions
How is pregnancy week calculated?+
It counts the weeks since your last menstrual period (LMP).
What if I don’t know my LMP?+
Use your best estimate or consult your healthcare provider for dating.
Are the tips medical advice?+
No. They are general guidance only.
Is my data stored?+
No. All calculations are done in your browser.
Key Features
- Calculate pregnancy week
- Trimester stage display
- Baby growth information
- Development milestones
- Week by week guide
- Due date calculation
- Pregnancy calendar
Benefits
Pregnancy Week Calculator runs without installing desktop software
Accepts: LMP or current gestational info
Returns: Week number + trimester label
When to Use Pregnancy Week Calculator
- When you need maps LMP or a given date to gestational week and trimester. without another app
- When your input looks like: LMP or current gestational info
Advantages
- Pregnancy Week Calculator runs without installing desktop software
- Accepts: LMP or current gestational info
- Returns: Week number + trimester label
- How-to and FAQs for Pregnancy Week Calculator live on the same page
Tips
- Read the Privacy & processing note before you paste secrets.
- Mixing embryonic age with gestational age (gestational is ~2 weeks ahead).
- Contact a clinician if symptoms are severe or unusual — online tools cannot triage emergencies.
Common Mistakes
Mixing embryonic age with gestational age (gestational is ~2 weeks ahead).
Treating one run as final without checking units or a second sample.
Ignoring related tools when the next step is resize, compress, or convert.
Summary
Use Pregnancy Week Calculator on this page, then browse related pregnancy tools linked below.