ToolsCalculators
Pregnancy Due Dates Calculator
Gestational age and time to estimated due date from the last menstrual period.
Pregnancy Due Dates Calculator
Days since first day of last menstrual period
days
Average cycle length
days
Complete the fields above to see the result.
When to use
- Estimating gestational age and the estimated due date from a certain last menstrual period.
Formula
Naegele's rule: estimated due date = LMP + 280 days, adjusted by (cycle length - 28) days. Gestational age = days elapsed since the first day of the LMP.
Pearls and pitfalls
- Assumes a certain LMP; first-trimester ultrasound is more accurate when dates are uncertain.
- Cycle-length adjustment shifts the due date for cycles that differ from 28 days.