🤰 Pregnancy / Gestational Age Calculator
Enter the first day of your last menstrual period (LMP) to see your current gestational age in weeks and days, which trimester you're in, and your estimated due date.
Based on first day of last menstrual period (LMP). Estimate only — confirm with your provider.
How the Pregnancy / Gestational Age Calculator works
Using the standard obstetric dating method, gestational age is counted as the days elapsed since the first day of your LMP, with the due date estimated as 280 days (40 weeks) after that date.
Step-by-step calculation
- 1Enter the first day of your last period.
- 2Count days since then.
- 3Convert to weeks and days and find the due date.
Worked example
With a last period on September 1, 2026, on November 14, 2026 you are 10 weeks 4 days pregnant, due June 8, 2027.
Pregnancy / Gestational Age Calculator examples
| First day of last period | Gestational age today |
|---|---|
| Dec 1, 2025 | 4 weeks, 3 days |
| Oct 15, 2025 | 11 weeks, 1 days |
| Aug 1, 2025 | 21 weeks, 6 days |
| May 15, 2025 | 33 weeks, 0 days |
| Apr 10, 2025 | 38 weeks, 0 days |
Calculated as of January 1, 2026. Other inputs kept at the calculator's default values. Results calculated by this calculator.
Why use a Pregnancy / Gestational Age Calculator?
Know how far along you are and your trimester.
Important factors that can affect your results
- Irregular cycles.
- Ultrasound dating.
- IVF dates use transfer day.
Frequently asked questions
Is this the same as fetal age?
No — gestational age (LMP-based) is the standard clinical convention and runs about 2 weeks ahead of actual fetal/conceptional age.
Could an ultrasound due date be different from this estimate?
Yes — an ultrasound-based due date is often more accurate than the standard LMP calculation and should take precedence if you have one.
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Last reviewed November 2026 · How we build and check our tools · Report a problem