A walkthrough, end to end.
- 1
Pick your input method: LMP, conception date, or known due date.
- 2
Enter the relevant date. The calculator computes gestational age (weeks + days) and the rest of the timeline.
- 3
Read your trimester boundaries and key milestones — first prenatal visit, NIPT, anatomy scan, glucose test, viability.
Gestational age
Gestational age is measured from the first day of your last menstrual period — not from conception, which happens about 2 weeks later. A full-term pregnancy is 40 weeks (280 days) by LMP, equivalent to 38 weeks post-conception.
What you can do with this.
Tracking gestational age week by week
Knowing 'I'm 14w3d' helps you cross-reference what's happening developmentally and what screening is upcoming. Most pregnancy resources are organized by gestational week.
Pregnancy by conception date
If you know the exact day of conception (IVF transfer + 5 days, or precisely-tracked ovulation), the calculator works backward to LMP and forward to due date with higher precision than LMP estimates.
Pregnancy by ultrasound
If a first-trimester ultrasound dated your pregnancy at e.g. 8w2d on a specific date, enter that to anchor the timeline. Early ultrasound is the most accurate dating method.
Key milestone windows
NIPT/cell-free DNA: 10w0d onward. Nuchal translucency: 11w0d–13w6d. Anatomy scan: 18–22w. Glucose tolerance: 24–28w. GBS swab: 36–37w. Knowing your dates helps you schedule.
Frequently asked.
Gestational age is measured from LMP. Fetal (or embryonic) age is measured from conception, ~2 weeks later. Clinical pregnancy weeks are gestational age.
If your provider has revised your dates with an early ultrasound, use those — they're more accurate, especially with irregular cycles.
ACOG defines 'full term' as 39w0d–40w6d. 'Early term' is 37w0d–38w6d, 'late term' is 41w0d–41w6d, 'post-term' is 42w0d+.
No — calculations run entirely in your browser.