Due Date Calculator
Estimate your baby's due date from your last menstrual period or conception date, with trimester milestones and your current week of pregnancy.
Estimated Due Date
February 10, 2027
Summary
Based on a last period date of May 6, 2026, the estimated due date is February 10, 2027 — currently 8 weeks and 4 days along, in the first trimester.
Current Week
8 w 4 d
Current Trimester
1 of 3
Pregnancy progress, out of 40 weeks
- Elapsed: 8 weeks
- Remaining: 32 weeks
How Is a Due Date Estimated?
Childbirth usually occurs approximately 38 weeks after conception, or about 40 weeks after the first day of the last menstrual period — the standard reference point doctors use since conception date is rarely known precisely. This convention is known as Naegele's Rule, adjusted for cycle length when it differs from the average 28 days.
A due date is only an estimate. The World Health Organization considers a pregnancy full term anywhere from 37 to 42 weeks, and fewer than 4% of babies are actually born on their exact due date — about 60% arrive within a week of it, and nearly 90% within two weeks.
Key pregnancy milestones
| Milestone | Week | Estimated Date |
|---|---|---|
| End of First Trimester | 13 | Aug 5, 2026 |
| Anatomy Scan (~Week 20) | 20 | Sep 23, 2026 |
| Viability (~Week 24) | 24 | Oct 21, 2026 |
| Third Trimester Begins | 28 | Nov 18, 2026 |
| Full Term (Week 37) | 37 | Jan 20, 2027 |
| Estimated Due Date | 40 | Feb 10, 2027 |
The Two Ways to Estimate a Due Date
Most due dates are calculated from the last menstrual period (LMP), since it's a date almost everyone knows, even though ovulation and conception typically happen about two weeks later. When the exact conception date is known — for example from fertility tracking — it can be used directly, adding 266 days (38 weeks) instead of 280.
Why Cycle Length Matters
The 280-day estimate assumes a 28-day cycle with ovulation around day 14. Longer cycles push ovulation — and therefore conception — later, which shifts the due date later too; shorter cycles shift it earlier. This is why the calculator asks for average cycle length rather than using a flat 280-day rule for everyone.
The Three Trimesters
Pregnancy is conventionally divided into three trimesters: the first covers weeks 1-13 and is when most early development and the highest miscarriage risk occurs; the second, weeks 14-27, is often considered the most comfortable; the third, weeks 28-40, is when the baby gains most of its birth weight and the body prepares for labor.
Example — Your Current Inputs
Based on a last period date of May 6, 2026, the estimated due date is February 10, 2027 — currently 8 weeks and 4 days along, in the first trimester.
Additional Example — A 35-Day Cycle
Someone with a last period date of January 1 and a typical 28-day cycle would have an estimated due date of October 8. With a longer 35-day cycle instead, the same last period date shifts the estimated due date to October 15 — a full week later, purely from the longer cycle.
Frequently Asked Questions
How accurate is a due date estimate?
Not very precise on any single day — fewer than 4% of babies are born exactly on their due date. It's best treated as the middle of a normal delivery window spanning roughly 37 to 42 weeks, rather than a firm deadline.
Is an ultrasound more accurate than the LMP method?
Early first-trimester ultrasounds are generally considered the most accurate dating method, since they measure the embryo's actual size rather than relying on memory of the last period or assumed ovulation timing. This calculator does not include ultrasound-based dating.
Why do LMP and conception dating give different results?
Gestational age (from LMP) and conception age differ by about two weeks, since ovulation and fertilization typically occur roughly 14 days after the last period begins. Both methods should point to the same due date once that two-week offset is accounted for.