What is Pregnancy Calculator?
A week-by-week pregnancy calculator translates your gestational calendar into clinical trimesters, fetal anatomy milestones, and screening timelines.
How to Use This Calculator
- Enter the date of your last menstrual cycle.
- Review your exact gestational week, day, and trimester classification.
- Learn baby development benchmarks for your current week.
The Mathematical Formula & Variables
Weeks = (CurrentDate - LMP) / 7; Trimester 1 (W1-13), Trimester 2 (W14-27), Trimester 3 (W28-40+)
Variables Definition
| Symbol / Variable | Name | Description |
|---|---|---|
Trimesters |
Three Stages | Standardized 13-week developmental periods. |
Step-by-Step Worked Example
Scenario: LMP began January 1, 2026; checking on April 9, 2026 (98 days elapsed).
- Total days = 98 days.
- 98 / 7 = exactly 14 weeks 0 days.
- Status: Officially entering the Second Trimester.
Result: 14 Weeks Pregnant (Second Trimester)
Frequently Asked Questions
Why does pregnancy dating start before conception happens?
Because the exact moment of ovulation and conception is rarely known with certainty, obstetricians universally date pregnancy from the start of the last menstrual period, approximately two weeks prior to fertilization.