Obstetrics
Gestational age
This gives the current gestation in completed weeks and days, from either the last menstrual period or a known due date. It is the number every antenatal decision is indexed against.
Enter the values
Keep going, every field is needed.
This calculator shows nothing until it has everything it needs. A half-answered score is a wrong score.
This calculator is provided for reference and education. It does not replace clinical assessment, examination, current guidelines, local protocol, or professional judgment. Verify every result before acting on it. Nirogix accepts no liability for clinical decisions made using this tool.
The formula
- From LMP: gestation (days) = today − first day of the last menstrual period
- From EDD: gestation (days) = 280 − (EDD − today)
- Reported as completed weeks and days
When to use it
- At every antenatal contact
- Interpreting a growth scan or planning delivery
And when not to
- Accuracy is only as good as the dating. An unreliable last menstrual period gives an unreliable gestation.
- Term definitions matter clinically: early term (37+0 to 38+6) is not the same as full term.
References
- Definition of term pregnancy — ACOG Committee Opinion 579, 2013
Last reviewed 07/09/2026.
These calculators are free and always will be. We also build Nirogix, a hospital management system for Indian clinics and hospitals. The same calculations are planned inside the consultation record, pre-filled from the chart.