Understanding Your Fertility Timeline
Conception is a game of timing. Unlike men who are fertile every day, women have a brief window of about 6 days per cycle where pregnancy is possible. This calculator helps you pinpoint that window to maximize your chances.
⚠️ How We Calculate
This tool uses the Standard Days Method. It subtracts 14 days from your estimated next period start date. While statistically accurate for about 70-80% of women, stress, illness, or hormonal conditions (like PCOS) can shift ovulation.
How to Use the Ovulation Calculator (Quick Steps)
- Enter your LMP (the first day of your last period).
- Enter your cycle length (or a min/max range if your cycles are irregular).
- Adjust luteal phase if you know it (average is 14 days; common range is 11–17).
- Check your fertile window (best odds are usually the 2 days before ovulation + ovulation day).
- Use the calendar to plan intercourse, OPK testing, and pregnancy test timing.
The 3 Phases of Conception
1. The Fertile Window
Sperm are resilient survivors—they can live in the uterus for up to 5 days. The egg, however, is fragile and lives only 12-24 hours. Your "fertile window" is the 5 days leading up to ovulation plus the day of ovulation itself.
2. Ovulation
Triggered by a surge in Luteinizing Hormone (LH), the ovary releases an egg. If sperm are already waiting (from intercourse days prior), fertilization can happen immediately.
3. Implantation
A fertilized egg travels down the fallopian tube and implants into the uterine lining. This typically happens 6 to 12 days past ovulation (DPO). This is why you can't take a pregnancy test immediately after sex—the hormone hCG isn't produced until after implantation.
Ovulation by Cycle Length (Table)
A common question is “when do I ovulate?” In many regular cycles, ovulation happens about 14 days before the next period. This table shows a quick estimate (assumes a 14‑day luteal phase):
| Cycle length | Estimated ovulation day | Typical fertile window (days) |
|---|---|---|
| 21 days | Day 7 | 2–7 |
| 24 days | Day 10 | 5–10 |
| 26 days | Day 12 | 7–12 |
| 28 days | Day 14 | 9–14 |
| 30 days | Day 16 | 11–16 |
| 32 days | Day 18 | 13–18 |
| 35 days | Day 21 | 16–21 |
If your luteal phase isn’t 14 days, your true ovulation can be earlier/later. That’s why this calculator lets you adjust it.
DPO Timeline: Implantation & Pregnancy Test Timing (Table)
People often search “implantation day” and “when to take a pregnancy test”. Here’s the typical timeline in DPO (days past ovulation):
| DPO | What can happen | What to do |
|---|---|---|
| 0 | Ovulation (egg released). | Best odds are 0–2 days before + ovulation day. |
| 1–5 | Fertilized egg travels toward the uterus (if conception happened). | Testing now is too early. |
| 6–12 | Implantation window (most common ~9 DPO). | Some people notice spotting/cramps, many do not. |
| 10 | Earliest hCG may be detectable in some pregnancies. | You can test, but false negatives are common. |
| 12 | Higher chance of detection vs very early testing. | Recommended time to test if you can’t wait. |
| 14 | Missed period day in many cycles. | Most accurate time to take a home test. |
3 Popular Ovulation Facts (Frequently Googled)
Can you ovulate right after your period?
Yes — especially with short cycles (e.g., 21–24 days) or long bleeding. Sperm can survive up to ~5 days, so intercourse near the end of a period can overlap with early ovulation.
How long does the egg live after ovulation?
Usually 12–24 hours. That’s why the highest pregnancy chances are typically the day before ovulation and ovulation day — not days after.
When should I start OPK (LH) testing?
A good rule is 3–5 days before predicted ovulation. A positive OPK often happens 24–36 hours before ovulation, but timing varies.
Myth Busting: The "Shettles Method"
You may have heard that timing sex can influence the gender of your baby (e.g., sex closer to ovulation for a boy, earlier for a girl). This is known as the Shettles Method.
The Reality: Modern studies largely debunk this. Evidence suggests that the timing of intercourse has no statistically significant impact on the sex of the baby. The odds remain roughly 50/50 regardless of timing.
When Should I See a Doctor?
If you are under 35 and have been trying to conceive for 12 months without success, it is recommended to see a fertility specialist. If you are over 35, the recommendation drops to 6 months. Once you confirm pregnancy, use our pregnancy due date calculator to estimate your delivery date.
Related Tools
- Period Calculator & Cycle Tracker — predict next period and cycle phases.
- Due Date Calculator — estimate delivery date once pregnancy is confirmed.