Pregnancy Due Date
Calculator
Results
- Estimated due date
- 2026-10-08
- Estimated gestational start
- 2026-01-01
Estimated pregnancy timeline
- 0 Last menstrual period start2026-01-01
- 13 13 weeks2026-04-02
- 20 20 weeks2026-05-21
- 37 37 weeks2026-09-17
- 40 Estimated due date2026-10-08
Estimated pregnancy milestones
| Last menstrual period start | 2026-01-01 |
| 13 weeks | 2026-04-02 |
| 20 weeks | 2026-05-21 |
| 37 weeks | 2026-09-17 |
| Estimated due date | 2026-10-08 |
Formula
EDD = LMP + 280 d= 2026-10-08
Note
This is an estimate, not clinical dating. Early ultrasound and obstetric assessment can confirm or supersede an LMP-based date.
More in Health
See all →Frequently asked questions
How is my due date calculated from my last menstrual period?+
The most common method, Naegele's rule, adds 280 days (40 weeks) to the first day of your last menstrual period, assuming a typical 28-day cycle with ovulation around day 14. This gives an estimated date, not a guaranteed delivery date.
Why might my due date change after an ultrasound?+
Early ultrasound measurements of the fetus are often considered more accurate than last-period dating, especially if your cycle length is irregular or you're unsure of your last period's exact start date. Doctors frequently adjust the estimated due date based on first-trimester ultrasound findings.
How accurate is a due date really?+
Only a small percentage of babies are born exactly on their calculated due date; most births occur within a window of about two weeks before to two weeks after it. The due date is best understood as the midpoint of a normal range, not a precise prediction.
Does the calculation change if my cycle isn't exactly 28 days?+
Yes, if your cycles are consistently longer or shorter than 28 days, the standard formula can be off, since it assumes ovulation on day 14. Some calculators let you input your typical cycle length to adjust the estimate accordingly.
What is the difference between gestational age and fetal age?+
Gestational age counts from the first day of your last menstrual period and is what's used clinically, while fetal (conceptional) age counts from the estimated date of conception, typically about two weeks later. This is why you may hear two different week counts referring to the same pregnancy.