Pregnancy Week Calculator
Find out exactly how many weeks and days pregnant you are, from your last menstrual period.
- Free to use
- Accurate results
- No registration required
- Works on all devices
Your result
14 weeks
Weeks pregnant
AI explanation
Formula
Current week = days since last period / 7, using whole weeks and remainder daysWorked example
LMP 2026-01-01, 10 weeks later
| Field | Value |
|---|---|
| First day of last menstrual period | 01-01-2026 |
| As of date | 12-03-2026 |
| Weeks pregnant | 10 |
| Plus days | 0 |
Assumptions
- Uses Naegele's rule conventions (a 28-day cycle assumption) for consistency with the due date calculation.
- Informational only — always confirm your pregnancy progress with your healthcare provider.
Frequently asked questions
How is "weeks pregnant" counted?
Pregnancy is counted from the first day of your last menstrual period, not from conception — so you're already considered about 2 weeks pregnant around the time of ovulation.
Why does my doctor's estimate differ slightly from this calculator?
Your doctor may use an ultrasound-based dating instead of menstrual dating, which can shift the estimated week by a few days if your cycle isn't exactly 28 days.
How many weeks is a full-term pregnancy?
A full-term pregnancy is considered 39-40 weeks, though anywhere from 37 to 42 weeks is generally considered within the normal range.
Related calculators
Sources
- Methods for Estimating the Due Date — American College of Obstetricians and Gynecologists (ACOG). Effective 01-05-2017, reviewed 13-09-2026.
This calculator provides a general estimate only and does not constitute personalized medical advice. Always confirm your pregnancy progress with a qualified healthcare provider.
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