Pregnancy & Fertility
Fertility Window Calculator
There are only about six days per cycle when conception is possible. Pin them down and time attempts for the best odds.
The fertile window is the roughly six days each cycle when pregnancy is possible: the five days before ovulation and ovulation day itself, because sperm survive up to five days but the egg survives only 12–24 hours. Dates are estimates — confirm timing with your provider and ultrasound where relevant.
6 fertile days per cycle.
Best odds: day of & 2 days before ovulation.
Sperm live ~5 days; egg ~24 hours.
Calculate Your Fertility Window
Fertile Days
What Is Fertility Window?
Pregnancy is only possible during the fertile window: the five days before ovulation plus ovulation day. Sperm can survive up to five days in the reproductive tract; the egg lives only 12–24 hours.
For couples trying to conceive, intercourse every 1–2 days across the window, especially the two days before ovulation, maximizes the odds.
How It Is Calculated
Fertile window = ovulation day − 5 … ovulation day + 1
Example: Example: 28-day cycle, LMP Aug 1 → peak days Aug 13–15, window Aug 10–16
Conception odds by timing (per cycle, healthy couples)
| Timing | Approximate odds |
|---|---|
| Intercourse on peak days | 25–30% |
| Intercourse 3+ days before ovulation | < 10% |
| After ovulation | ≈ 0% |
| Any timing, full cycle | ~20–25% |
Limitations
- Calendar estimates assume a regular cycle.
- Ovulation varies month to month, confirm with OPKs or BBT.
- Most healthy couples conceive within 6–12 cycles; evaluation is recommended after 12 months (6 if 35+).
Sources & Review
References used for this calculator’s formulas and thresholds:
Fertility Window FAQ
When is the best day to get pregnant?
The day of ovulation and the two days before, the egg is only viable 12–24 hours, but sperm wait for it.
How do I confirm ovulation?
LH test strips turn positive 24–36 hours before ovulation; a sustained BBT rise confirms it after the fact.
How long should we try before seeking help?
12 months under 35, 6 months if 35+, or sooner with irregular cycles or known conditions.
Does stress affect the fertile window?
Yes, stress can delay ovulation by days or weeks, shifting the whole window later.
Please read this first: these results are educational estimates, not medical advice. For decisions about your health, talk to a qualified professional.