Due Date Calculator
Estimate your due date from the first day of your last menstrual period and cycle length. Get the date range and current gestational age.
About this tool
This due date calculator estimates your pregnancy due date using the classic Naegele rule: add 280 days to the first day of your last menstrual period, adjusted by your typical cycle length. It also shows the standard ±2-week delivery window and your current gestational age.
Most pregnancies last between 38 and 42 weeks, and only a small fraction land on the exact predicted date — use it for planning, not accuracy promises. For medical care and dating scans, always follow your obstetrician's guidance.
FAQ
How is the due date calculated?
The standard Naegele rule adds 280 days (40 weeks) to the first day of your last menstrual period. Cycle length adjusts the estimate slightly.
Is the due date exact?
Very rarely. Only about 4% of babies arrive on the exact date — the majority arrive within two weeks before or after.
What if my cycle is irregular?
An ultrasound dating scan in the first trimester is more accurate. Use this calculator as an approximate planning reference.