gestational age calculator

What is gestational age?

Gestational age is the standard way healthcare professionals describe how far along a pregnancy is. It is usually measured in weeks and days, starting from the first day of your last menstrual period (LMP), not from the day of conception.

This approach is used because LMP is often easier to identify than exact conception timing. In a typical cycle, conception happens about 2 weeks after LMP, which is why early pregnancy may be described as 4 weeks pregnant even though conception happened roughly 2 weeks earlier.

How this gestational age calculator works

This calculator supports three common methods:

• From LMP: Gestational age = date difference between LMP and your selected “as of” date.
• From due date (EDD): LMP is estimated by subtracting 280 days (40 weeks) from EDD.
• From conception date: LMP is estimated by subtracting 14 days from conception date.

After calculation, you’ll see your current gestational age, trimester, estimated due date, and days remaining until due date (or days overdue if past EDD).

Understanding the results

Gestational age in weeks + days

Pregnancy duration is commonly shared as X weeks and Y days. For example, 23 weeks and 4 days is written as 23w4d. This format gives more precision than weeks alone and is commonly used in prenatal visits, ultrasound reports, and pregnancy records.

Estimated due date (EDD)

The due date is an estimate based on a 40-week pregnancy. Most pregnancies naturally deliver within a range around this date. Being a few days before or after due date is very common.

Trimester stage

• First trimester: 0 weeks to 13 weeks + 6 days
• Second trimester: 14 weeks to 27 weeks + 6 days
• Third trimester: 28 weeks onward

Why your doctor’s dating might differ

It is normal for estimated dates to change slightly, especially early in pregnancy. Clinicians may adjust gestational age using first-trimester ultrasound measurements when those are more accurate than menstrual dating.

• Irregular menstrual cycles
• Uncertain LMP date
• Late ovulation
• Early ultrasound findings

If your app, calendar, and clinic notes show different numbers, rely on your clinician’s official dating for medical decisions.

Tips for more accurate pregnancy date tracking

• Use the exact first day of bleeding for LMP (not spotting).
• Use a reliable “as of” date when checking progress.
• If known, compare LMP-based and due-date-based calculations.
• Save your results so you can monitor week-by-week changes.

Important medical note

This gestational age calculator is for educational and planning purposes. It is not a diagnostic tool and does not replace prenatal care. If you have pain, bleeding, concerns about fetal movement, or questions about your pregnancy timeline, contact a qualified healthcare professional immediately.