Estimate when you conceived, your due date, gestational age, and current trimester from your last menstrual period (LMP).
Estimated conception dates are shown as an approximate two-week window for each example due date.
| Due date | Estimated conception | Window |
|---|---|---|
| 2027-03-08 | Around 2026-06-21 | 2-week range |
| 2027-06-11 | Around 2026-09-23 | 2-week range |
| 2027-01-15 | Around 2026-04-30 | 2-week range |
| 2026-12-25 | Around 2026-04-15 | 2-week range |
| 2026-11-10 | Around 2026-02-28 | 2-week range |
Conception typically 11–21 days after LMP for 28-day cycles. ACOG.
A conception calculator estimates when conception most likely occurred from the first day of your last menstrual period (LMP) and your average cycle length. Conception typically happens on the day of ovulation, which is about 14 days before the next period in a 28-day cycle. The calculator also projects the estimated due date using Naegele's rule (LMP + 280 days), current gestational age, current trimester, and key pregnancy milestones from week 6 through full term.
The first day of bleeding before pregnancy
Jul 22, 2026
Apr 14, 2027
1 of 3
Today: 10 weeks 0 days pregnant (gestational age) — 210 days until due date
| Week | Date | Milestone |
|---|---|---|
| 6 | Aug 19, 2026 | Heartbeat detectable on ultrasound |
| 13 | Oct 7, 2026 | End of first trimester |
| 20 | Nov 25, 2026 | Anatomy scan (typically scheduled) |
| 24 | Dec 23, 2026 | Viability (chance of survival if born) |
| 27 | Jan 13, 2027 | End of second trimester |
| 37 | Mar 24, 2027 | Full term begins |
| 40 | Apr 14, 2027 | Estimated due date |
| 41 | Apr 21, 2027 | Late term |
Conception estimates assume a 14-day luteal phase. Due date uses Naegele's rule (LMP + 280 days) — only about 5% of babies are born exactly on the due date, with most arriving within 2 weeks before or after. Ultrasound dating in the first trimester is more accurate than LMP-based calculation.
Cross-checked against authoritative formulas (IRS, NIST, ACSM) and updated for 2025/2026 tax years and rates.
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FAQ
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A conception calculator is a free pregnancy planning tool that estimates when conception most likely occurred and projects the due date. Our conception calculator takes the first day of your last menstrual period (LMP) and your average cycle length, then estimates the conception date (around ovulation, which is typically 14 days before the next period), the due date using Naegele's rule (LMP + 280 days), and the current gestational age and trimester.
How it works
Our conception calculator estimates when conception most likely occurred and projects your due date using Naegele's rule.
Pick the first day of bleeding from the period before pregnancy. The conception calculator uses this as the reference point for both conception date and due date.
Type your average cycle length in days. 28 is standard; longer or shorter cycles shift the conception date. Our conception calculator uses this to compute when ovulation likely occurred.
The conception calculator shows the estimated conception date (ovulation day), the estimated due date (LMP + 280 days), current gestational age (weeks and days), current trimester, and a calendar of key pregnancy milestones from week 6 through full term.
Estimate fertile window and ovulation day from your cycle.
Estimate your due date and current week from your last period.
Track your pregnancy week by week and key milestones.
Predict your next period, fertile window, and PMS dates from your cycle history.