按末次月经和周期长度推算排卵日、最易受孕窗口和预产期。
The first day of bleeding before pregnancy
Sep 12, 2026
Jun 5, 2027
1 of 3
Today: 10 weeks 0 days pregnant (gestational age) — 210 days until due date
| Week | Date | Milestone |
|---|---|---|
| 6 | Oct 10, 2026 | Heartbeat detectable on ultrasound |
| 13 | Nov 28, 2026 | End of first trimester |
| 20 | Jan 16, 2027 | Anatomy scan (typically scheduled) |
| 24 | Feb 13, 2027 | Viability (chance of survival if born) |
| 27 | Mar 6, 2027 | End of second trimester |
| 37 | May 15, 2027 | Full term begins |
| 40 | Jun 5, 2027 | Estimated due date |
| 41 | Jun 12, 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.
排卵在下次月经前 14 天，受孕窗口是排卵前 5 天至排卵后 1 天：
| 周期天数 | 排卵日 | 受孕窗口 | 预产期（排卵+266天） |
|---|---|---|---|
| 21 天 | 第 7 天 | 第 2-8 天 | 第 273 天 |
| 28 天 | 第 14 天 | 第 9-15 天 | 第 280 天 |
| 35 天 | 第 21 天 | 第 16-22 天 | 第 287 天 |
卵子排出后 12-24 小时可受精。精子可在体内存活 5 天。每个周期怀孕概率约 20-25%。周期长度变化 > 7 天建议就医。
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.
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