Find your probability of conceiving based on age and history.
Enter your age and history on the left to see your success probability.
👉 Success Tip: While our calculator estimates your probability, using an ovulation tracker is the only way to catch your actual LH surge and confirm you are timing intimacy correctly.
Track your LH surge and time intercourse perfectly. Includes 50 ovulation strips and 20 pregnancy tests.
View on AmazonOur calculation uses peer-reviewed research to estimate probability based on timing, age, and cycle length. Peak conception happens 1-2 days before ovulation.
Two women who are both 35 can have pregnancy odds that differ by a factor of three. Age on a birth certificate predicts average population-level fertility. These markers predict yours.
| Biological Factor | How It's Assessed | Impact on Calculator Estimate | Direction of Effect |
|---|---|---|---|
| AMH (Anti-Müllerian Hormone) | Blood test (any time in cycle) | High | Low AMH → reduce estimated chance. High AMH → increase it. |
| AFC (Antral Follicle Count) | Transvaginal ultrasound (Day 2–5) | High | Corroborates AMH. <5 follicles = diminished reserve regardless of age. |
| BMI extremes (<18.5 or >35) | Calculated from height/weight | Medium | Both extremes suppress LH pulsatility and disrupt ovulation. Compounds age-related decline. |
| Age at menarche | Patient history | Low–Medium | Early onset (<12) correlates with earlier decline. Late onset often predicts extended fertility window. |
| Thyroid function (TSH) | Blood test (TSH, free T4) | Medium | TSH above 2.5 mIU/L suppresses implantation and increases early loss risk. Easily corrected with medication. |
Every pregnancy chance calculator — including this one — calculates probability based on female age and cycle timing. But conception is a two-person event. Here is what the male side of the equation looks like, and why it matters as much as your fertile window.
The 12-month guideline before seeking specialist help is a population-level recommendation written primarily for women under 35 with no known risk factors. For a significant proportion of people using this calculator, following it without question delays diagnosis of a treatable problem.
Standard advice applies. Try for 12 months with correctly-timed intercourse before requesting a fertility referral. At 6 months, consider basic hormone blood tests with your GP.
At least one exception applies to your situation. The 12-month rule may not be appropriate. Review the specific scenarios below to find your recommended timeline.
ACOG guidelines explicitly reduce the waiting period to 6 months for women 35–39. AMH declines approximately 0.1–0.2 ng/mL per year — a 12-month delay is not clinically neutral at this age.
→ See specialist at 6 monthsACOG recommends immediate evaluation without any waiting period at age 40+. Every cycle has meaningful value; time lost to the "wait and see" approach is not recoverable at this stage.
→ See specialist immediatelyCycle irregularity is a clinical signal of potential ovulatory dysfunction — the most common treatable cause of female infertility. Waiting 12 months simply confirms what testing can identify in week one.
→ See specialist without waitingChlamydia causes tubal scarring with no symptoms in approximately 75% of cases. Tubal factor accounts for 25–30% of female infertility. A hysterosalpingogram (HSG) can confirm tubal patency before trying.
→ Request HSG before month 1Recurrent pregnancy loss (RPL) investigation is clinically indicated after two losses regardless of how quickly conception occurred. The ability to conceive does not eliminate the need for investigation.
→ Recurrent loss panel after 2nd lossIf a prior semen analysis showed any abnormality — even borderline — the 12-month rule does not apply. Known male factor justifies immediate referral, not monitoring for a year while the female partner tracks cycles.
→ Joint referral immediately"Every cycle gives us a fresh 20–25% chance — like rolling the dice again from zero."
Your monthly fecundability rate is personal and stable, not a reset button. If you've had 8 failed cycles, it doesn't mean you're "due" for success — it may indicate your personal rate is 8–10%, not the population average of 20–25%. Each cycle is an independent event with your constant individual probability, not a collective improvement toward a guaranteed outcome.
The Weinberg-Wilcox cumulative conception model explains why some couples take longer — not because luck hasn't arrived, but because their personal p is lower than the average.
"Having sex every single day during the fertile window gives you the maximum possible chance."
Daily intercourse does not significantly outperform every-other-day intercourse in couples with normal semen parameters. In men with borderline motility or morphology, daily ejaculation during the fertile window may reduce per-encounter sperm quality below what every-other-day spacing would produce. The optimal frequency is every 1–2 days during the fertile window — not maximising frequency.
Multiple RCTs and WHO guidance on timed intercourse support the every-other-day approach as equivalent or superior in borderline male factor cases.
"Stress is preventing you from getting pregnant. You just need to relax and it'll happen."
Only clinically severe, chronic stress — such as that from major trauma, extreme athletic training, or severe eating disorders — measurably suppresses LH pulsatility and disrupts ovulation. Everyday work stress, relationship anxiety, or the stress of trying to conceive itself does not demonstrate statistically significant impact on conception rates in controlled studies. The "just relax" advice misattributes a biological problem to a psychological one and removes responsibility from investigation.
Lynch et al. (2014) and multiple systematic reviews found no association between self-reported stress and fecundability in normally cycling women.
"Certain sexual positions after intercourse improve your chances because they help sperm travel better."
No peer-reviewed evidence supports any positional advantage. Sperm reach the cervix within 90 seconds of ejaculation regardless of position — they are motile cells driven by chemotaxis toward progesterone gradients, not passive particles affected by gravity. Post-coital lying down for 30 minutes shows no outcome difference in multiple RCTs. If lying still reduces stress and adds comfort, that's fine — but it provides no biological advantage.
Wilkes et al. (2003) found no difference in pregnancy rates between immediate activity and 15-minute supine rest post-IUI — and IUI deposits sperm directly at the cervix.
"A positive OPK (ovulation test) guarantees you will ovulate within 12–36 hours."
An LH surge detected by OPK can fail to result in actual ovulation — called an anovulatory LH surge — in approximately 7–8% of cycles in normally ovulating women. In women with PCOS, this false-positive rate is dramatically higher due to chronically elevated baseline LH, which makes OPKs nearly uninterpretable without ultrasound confirmation. The only way to confirm ovulation definitively is a Day 21 progesterone blood test or transvaginal ultrasound showing follicle collapse.
Anovulatory cycles are more common during stress, illness, or at the beginning and end of reproductive years, making OPK-only tracking unreliable in these periods.
The single percentage figure a calculator produces is a population average applied to your age bracket. Here is how clinicians build an individual probability model — and why the two numbers can be very different for the same person.
The fecundability rate defined: Your fecundability rate is not a fresh chance each month — it is a personal, stable probability per cycle that remains essentially constant assuming no change in underlying factors. The core insight is that the population average tells you nothing about where your individual rate sits.
The Weinberg-Wilcox cumulative probability formula
The clinical multiplier model: how each factor adjusts your base rate
| Factor | How It's Measured | Multiplier on Base Rate | What Changes the Multiplier |
|---|---|---|---|
| Base rate (age-adjusted) | Age alone (population average) | 1.0× (starting point) | Under 30: ~25%. 30–34: ~20%. 35–39: ~12–15%. 40+: ~5–8%. |
| Intercourse timing accuracy | OPK / BBT / cycle tracking | 0.8×–1.2× | Peak day (day before ovulation) = 1.2× modifier. Random untracked timing = 0.8× or lower. |
| Sperm quality (partner) | Full semen analysis + DFI | 0.3×–1.0× | Normal parameters = 1.0×. Mild male factor = 0.7×. Severe oligospermia or high DFI = 0.3× or below. |
| Ovarian reserve (AMH) | Blood test ng/mL | 0.5×–1.3× | AMH above age-normal = 1.1–1.3×. Diminished reserve (<1.0 ng/mL at 35) = 0.5–0.7×. |
| Uterine/tubal factor | Hysterosalpingogram (HSG), sono | 0× (blocked) – 1.0× | One blocked tube = ~0.5×. Both patent = 1.0×. Submucosal fibroid or polyp = 0.6–0.8×. |
| Thyroid/hormonal baseline | TSH, prolactin, Day 3 FSH/LH | 0.6×–1.0× | Elevated TSH (above 2.5) = 0.7×. Elevated prolactin = 0.5–0.8×. Easily corrected with medication. |
| BMI (both partners) | Height and weight | 0.7×–1.0× | BMI 20–25 = 1.0×. BMI above 35 or below 18.5 = 0.7–0.8× due to hormonal disruption. Modifiable. |
Cumulative at 6 months: ~58% | Cumulative at 12 months: ~82% | If AMH returns low (modifier 0.6×): drops to ~8.6% / cycle → 40% at 6 months, 65% at 12 months. This is why testing changes the decision about when to escalate.
Fertility statistics like "80% of couples conceive within 6 months" are based on population cohorts where couples who conceive early exit the study. Those who remain in the study pool are skewed toward lower fecundability — their continued presence is itself evidence of a lower personal rate. This is why the commonly cited statistics feel optimistic to couples who are actively trying and not yet successful: those statistics describe the population at month 1, not the sub-population at month 5. Your relevant comparison group shifts every month you try without success, and the calculator's static percentage does not account for this progressive selection effect.
This calculator estimates results based on average ovulation timing and reproductive biology.
Results are estimates and may vary based on individual health and cycle patterns.
For healthy couples under 35, the chance of getting pregnant in any single cycle is approximately 20–25%. This drops to around 15% per cycle at age 35–39, and about 5–10% per cycle at age 40 and above. Timing intercourse 1–2 days before ovulation significantly improves your odds.
Pregnancy chances vary significantly by age. Women under 30 have roughly 20–25% per cycle, ages 30–34 around 15–20%, ages 35–39 around 10–15%, and over 40 approximately 5% per cycle. Use our pregnancy chance calculator by age tool for a more detailed breakdown.
The day with the highest chance of conception is 1–2 days before ovulation, with around 25–30% probability per cycle for healthy couples. Ovulation day itself carries approximately 15–20% chance. Having intercourse every 1–2 days during the 5-day fertile window maximizes your overall chances.
You can estimate your pregnancy percentage chance by entering your last period date, cycle length, and when you had intercourse relative to ovulation into our calculator above. The calculator uses research-based probability data to give you a personalized percentage. Note: only a pregnancy test can confirm pregnancy.
The chance of getting pregnant from a single unprotected encounter depends entirely on where you are in your cycle. On your most fertile day (1–2 days before ovulation), the odds are around 25–30%. Outside the fertile window, chances drop to near 0%. Use the calculator above with your specific dates for an accurate estimate.
Pregnancy chance calculators provide statistical estimates based on population-level fertility research. They are useful for understanding your approximate odds but cannot account for individual health factors like PCOS, endometriosis, or sperm health. Always consult a doctor if you have been trying to conceive for 6–12 months without success.