👶 Due Date Calculator
Estimate your pregnancy due date based on your last menstrual period.
What is this tool?
Our Due Date Calculator estimates your pregnancy due date using your last menstrual period (LMP) and average cycle length. Pregnancy typically lasts about 40 weeks (280 days) from the first day of your LMP. This tool also estimates your conception date and shows how far along you are based on the current date.
How it works
The standard Naegele's Rule adds 280 days (40 weeks) to the first day of the last menstrual period. The calculator adjusts for cycle length: if your cycle is longer than 28 days, the due date shifts forward proportionally. The conception date is estimated as approximately 14 days after LMP (around ovulation), adjusted for cycle length.
How to use
- Select the first day of your last menstrual period using the date picker.
- Enter your average cycle length in days (default is 28).
- Click Calculate to see your estimated due date, conception date, and current pregnancy week.
Reference Table
| Cycle | LMP → Due | Adjustment |
|---|---|---|
| 28 days | 280 days | None |
| 30 days | 282 days | +2 days |
| 35 days | 287 days | +7 days |
| 21 days | 273 days | -7 days |
Frequently Asked Questions
How accurate is the due date?
Only about 5% of babies are born exactly on their due date. The estimate is most accurate for women with regular 28-day cycles and known LMP.
What if my cycles are irregular?
If your cycle length varies significantly, an early ultrasound measurement is more accurate for dating the pregnancy.
When is my baby due if I know the conception date?
Add 266 days (38 weeks) from the conception date to estimate the due date.
Tips & Advice
Schedule your first prenatal appointment soon after a positive pregnancy test. Keep track of your cycle lengths before pregnancy for the most accurate due date estimate. Remember that the due date is an estimate — full-term delivery can occur anywhere from 37 to 42 weeks.