Gestational Age Calculator: By LMP, Due Date, Ultrasound or IVF
Find the gestational age (weeks + days) of a pregnancy on any date, using the last period, a due date, an ultrasound result or an IVF transfer.
- Nothing you type is stored
- Free
- No signup
Gestational age
0weeks
1st trimester- In days
- 0 days
- Due date
- Wed, 11 Aug 2027
- Pregnancy counted from
- Wed, 4 Nov 2026
- Likely conception
- Wed, 18 Nov 2026
An estimate for general information, not medical advice. Dates can differ by a week or two; confirm with your doctor or ANM.
Counted from the first day of the last period (about 2 weeks before conception).
Dates for key weeks
| Week | Date |
|---|---|
| 8 | Wed, 30 Dec 2026 |
| 12 | Wed, 27 Jan 2027 |
| 20 | Wed, 24 Mar 2027 |
| 24 | Wed, 21 Apr 2027 |
| 28 | Wed, 19 May 2027 |
| 32 | Wed, 16 Jun 2027 |
| 36 | Wed, 14 Jul 2027 |
| 37 | Wed, 21 Jul 2027 |
| 39 | Wed, 4 Aug 2027 |
| 40 | Wed, 11 Aug 2027 |
| 41 | Wed, 18 Aug 2027 |
| 42 | Wed, 25 Aug 2027 |
How to use
- Choose the method: last period, due date, ultrasound or IVF.
- Enter the dates asked for (for a scan: the scan date and the age it showed).
- Pick the date you want the age for (today by default).
Good to know
Gestational age is counted from the first day of the last menstrual period (LMP), even when the pregnancy is dated by a scan. For an ultrasound, the start is the scan date minus the age shown on the report; for a due date, it is 280 days before the due date.
An early ultrasound, especially the first-trimester crown–rump length scan, is the most accurate way to date a pregnancy. Doctors usually keep that date even if later scans measure bigger or smaller.
Term categories (ACOG): early term 37w0d–38w6d, full term 39w0d–40w6d, late term 41w0d–41w6d, post-term from 42w0d. Before 37 weeks a birth is called preterm. These labels describe timing only; your doctor decides on care.
Questions
What is the difference between gestational age and fetal age?
Gestational age starts from the last period; fetal age starts at conception and is about 2 weeks less.
How do I use my ultrasound report?
Enter the scan date and the gestational age it shows (for example 12 weeks 3 days). The calculator works forward to any date.
Which is more accurate, LMP or ultrasound?
An early ultrasound is usually more accurate, especially if your cycles are irregular or you are unsure of the period date.
What does 39+0 mean?
39 weeks and 0 days of pregnancy, which is full term.
Is my data saved?
No. Dates are calculated on your device and never sent anywhere.