Gestational Age

What This Calculator Measures

Calculates gestational age in decimal weeks from entered weeks and days, and relates this to the weeks + days format clinicians commonly use in pregnancy.

How to Use

1. Enter the gestational age in completed weeks and days (e.g., 32 weeks 3 days).
2. The calculator returns gestational age as a decimal number of weeks (weeks + days/7).
3. Clinicians commonly express the same age as '32 weeks 3 days'; the decimal output (32.43 weeks) is the equivalent single number.
4. Clinical dating of pregnancy typically relies on the LMP or, when available, established ultrasound dating.

Interpretation Guide

The calculator returns gestational age in decimal weeks; for example, 32 weeks 3 days is reported as approximately 32.43 weeks. Clinically, gestational age is usually expressed in completed weeks plus days (e.g., 32w3d), and this decimal value is the mathematical equivalent. The calculator does not determine viability or obstetric diagnosis — that requires full clinical and ultrasound assessment.

Clinical Significance

Gestational age is the cornerstone of pregnancy dating and fetal growth assessment; expressing it consistently as weeks plus days (or a decimal equivalent) supports accurate documentation and interpretation of prenatal milestones.

When to Use

• Converting a weeks + days gestational age into a decimal number of weeks
• Educational review of gestational age reporting
• Supporting documentation and calculations that require gestational age in weeks

When Not to Use

• To determine pregnancy viability or fetal well-being
• To replace ultrasound-based dating when dating is uncertain
• As a substitute for clinical assessment or obstetric diagnosis

Limitations

• The calculator is a unit conversion (weeks + days/7); it does not compute gestational age from dates or from ultrasound measurements.
• Accuracy of the entered age depends on how pregnancy dating was established (LMP or ultrasound).
• The decimal output (e.g., 32.43 weeks) should not be mistaken for a new clinical estimate; it is the same age expressed differently.
• The calculator accepts 0–42 weeks and 0–6 days, matching its input limits.

Worked Example

A patient's gestational age is 32 weeks and 3 days.

Gestational age = 32 + 3/7 ≈ 32.43 weeks (32 weeks 3 days).

Evidence

Source

ACOG Committee Opinion

Reference

ACOG Committee Opinion No. 700: Methods for estimating the due date. Obstet Gynecol. 2017;129(5):e150-e154.

Reviewed By

MedCalcHub Clinical Team

Version

2017

Updated

2026-08

1. ACOG Committee Opinion No. 700. Obstet Gynecol. 2017;129(5):e150-e154.

References

1. ACOG Committee Opinion No. 700: Methods for estimating the due date. Obstet Gynecol. 2017;129(5):e150-e154. (Clinical guideline)