Estimate your babys due date from your last period, conception date, or ultrasound dating.
Estimated due dates (EDD) computed via Naegele's rule (LMP + 280 days), assuming a 28-day cycle.
| LMP (first day) | Estimated due date | Gestation at 20 weeks |
|---|---|---|
| Jan 1, 2026 | Oct 8, 2026 | May 20, 2026 |
| Apr 1, 2026 | Jan 6, 2027 | Aug 19, 2026 |
| Jul 1, 2026 | Apr 7, 2027 | Nov 18, 2026 |
| Oct 1, 2026 | Jul 8, 2027 | Feb 18, 2027 |
Source: ACOG Committee Opinion No. 700 (2017); Naegele's rule assumes 28-day cycle.
Calculate your estimated due date and trimester milestones
This calculator uses Naegele's Rule: add 280 days (40 weeks) to the first day of your last menstrual period, adjusted for your cycle length. This is the most widely used method for estimating due dates.
Note: Only about 4% of babies are born on their exact due date. Most arrive between 37-42 weeks. Your healthcare provider may adjust the due date based on ultrasound measurements.
Type the first day of your last period. This is the standard reference date used by most obstetricians.
Naegele's rule: due date = LMP + 280 days (40 weeks). The calculator also shows the date range (38-42 weeks is full term).
Get your current week, trimester, and key dates: first prenatal visit, anatomy scan, viability (24w), and full term (37w).
For related calculations, try our pregnancy calculator.
Cross-checked against authoritative formulas (IRS, NIST, ACSM) and updated for 2025/2026 tax years and rates.
No server roundtrip. All math runs in your browser so results appear the moment you finish typing.
We never collect, store, or transmit your inputs. Every calculation runs locally in your browser.
Each calculator includes the formula, plain-English explanation, and FAQs so you understand the result.
Estimates only. Calculator results are for educational and planning purposes — not professional advice. For binding decisions on taxes, investments, health, or legal matters, consult a qualified professional.
FAQ
Everything you need to know about this calculator. Can't find what you're looking for? Email our team.
A pregnancy due date calculator is a free tool that estimates when your baby will arrive based on your last menstrual period, conception date, or ultrasound dating. Our pregnancy due date calculator uses the Naegele rule plus adjustments for irregular cycles. The pregnancy due date calculator also shows a week-by-week timeline of fetal development milestones.
How it works
Our pregnancy due date calculator lets you estimate your baby's due date and current week of pregnancy using Naegele's Rule in three steps.
Type the first day of your last menstrual period (LMP). This is the anchor date for Naegele's Rule.
Type the typical length of your menstrual cycle in days. The default 28 days works for most people.
The calculator shows the estimated due date, your current week and trimester, and key milestone dates for each trimester.
Estimate your conception date and fertile window from your due date or last period.
Estimate fertile window and ovulation day from your cycle.
Track your pregnancy week by week and key milestones.
Find your recommended pregnancy weight gain by pre-pregnancy BMI per IOM guidelines.