Gestational Age
Calculate the current gestational age
Result
Gestational Age
Assessment date:
Gestational age in days:
Trimester:
ACOG classification:
Estimated due date:
Gestational Milestones
| Age | Milestone |
|---|---|
| 0 – 13 weeks | 1st trimester — organ formation |
| 14 – 27 weeks | 2nd trimester — growth and development |
| 28 – 40 weeks | 3rd trimester — maturation and weight gain |
| Prematurity classification | |
| < 28 weeks | Extremely preterm |
| 28 – 31 weeks | Very preterm |
| 32 – 36 weeks | Late preterm |
| Term classification by gestational age — ACOG | |
| 24 weeks | Threshold of fetal viability |
| 37 – 38 weeks | Early term |
| 39 – 40 weeks | Full term |
| 41 weeks | Late term |
| ≥ 42 weeks | Post-term |
How the Calculation Works
From LMP
Counts the number of days between the last menstrual period and the assessment date, converting to weeks and days. The EDD is calculated by adding 280 days to the LMP (Naegele's Rule).
From Conception Date
Subtracts 14 days from the conception date to obtain the equivalent LMP (average interval between menstruation and ovulation in 28-day cycles) and calculates from that point.
From EDD
Subtracts 280 days from the stated EDD to obtain the equivalent LMP, then calculates how many days of gestation have elapsed up to the assessment date.
Note: The calculation assumes regular 28-day menstrual cycles. For greater accuracy — especially with irregular cycles or when the LMP is uncertain — gestational dating by first-trimester ultrasound is recommended (ACOG). Always consult a healthcare professional.