Pregnancy Chance Calculator

Last updated Feb 8, 2026 | By

Get an instant estimate of your chance of pregnancy, based on published research and the details you enter.

Count any events you want to estimate for, regardless of time period.
Used to estimate baseline fertility and age-related risks. If blank, this uses 30.
Typical use is average real-world use. Perfect use means correct use every time. Learn more.
Second method
If you select perfect use here, the model assumes correct use every time for this second method.
Used as a fertility modifier. If blank, this uses 25.
If blank, the model uses an average height. Height and weight are used to estimate BMI.
If blank, the model uses an average weight.
Used as a small fertility modifier. If blank, this uses 0.
Used as a fertility modifier. If blank, this uses 0.
Used as a fertility modifier. If blank, this uses 0.
Peer-Reviewed Science
Updated Feb 2026
See Methodology
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How to Use Our Calculator

  1. Enter the number of intercourse events you want to estimate for (any time frame).
    Only one event? Try the One-Time Calculator.
  2. Enter your age (optional) and .
  3. Choose a contraceptive method (optional) - leave as “No contraceptive” if none was used.
  4. For a more accurate result, use the 'Advanced Settings' inputs. The more you use, the more precise our estimate will be.
  5. Press Calculate

We don’t store your inputs. Results are estimates and show a capped range (never exactly 0% or 100%).

A screenshot of the Simple Pregnancy Chance Calculator, showing input fields for contraceptive method and intercourse frequency.

How Our Calculators Work: The Science Behind Your Estimate

At Pregnancy Chance Calculator, we use proven mathematical models and data from dozens of peer-reviewed scientific studies to estimate your probability of conception.

Think of it like a weather forecast - it doesn’t predict outcomes with 100% certainty, but it gives you a science-backed probability based on real-world data.

The Key Factors in Our Algorithm

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Female Age

A primary driver of fertility. Our model accounts for the natural decline in egg quantity and quality over time, based on guidelines from the American College of Obstetricians and Gynecologists (ACOG).

👨

Male Age

Male fertility also declines with age, affecting sperm health. Our algorithm considers this factor, especially for partners over 40, as supported by research on paternal age.

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Intercourse Timing

We analyze the timing of intercourse relative to the fertile window, incorporating data showing that intercourse frequency can be more effective than targeted ovulation timing alone.

⚖️

Body Mass Index (BMI)

A healthy BMI is crucial for hormonal balance. Our calculations are adjusted based on studies linking BMI to fertility outcomes.

❤️

Lifestyle Factors

Our advanced models incorporate data on how choices like smoking or alcohol consumption can impact hormonal regulation and overall fertility.

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Contraceptive Use

We use large-scale study data, including the landmark Trussell (2011) study on contraceptive failure, to factor in typical and perfect-use rates.

Estimated Pregnancy Chance vs. Cigarette Intake chart.
An example of the impact of smoking on pregnancy chance; one of the many factors that we integrate into our calculators using peer-reviewed science.

Foundational Data Sources & Primary Research

For a complete list of the dozens of studies and data sets used in our models, please visit our full Research Library.

Frequently asked questions

How many days after my period will I conceive?
If your cycle is ~28 days, the fertile window is usually cycle days 10–15, with ovulation around day 14. If your cycles are shorter or longer, the window shifts. You can get pregnant soon after a period if you ovulate early. For a personalized window, try the Ovulation Calculator.
When is the 100% chance of getting pregnant?
There’s no time with a 100% chance. The highest odds are the 2–3 days before ovulation and ovulation day itself. After 12–24 hours post-ovulation, the chance for that cycle drops sharply. Use the Ovulation Calculator to see your most fertile days.
How can I be sure I ovulated?
Confirmation is retrospective: a sustained basal body temperature rise after ovulation, or ultrasound. OPKs show an LH surge but don’t prove ovulation by themselves. For help interpreting your data, see the BBT Ovulation Calculator and OPK→Ovulation Timing Calculator.
How reliable is the withdrawal method?
Typical-use effectiveness is about 78% over a year (roughly 22 pregnancies per 100 users). Effectiveness depends on perfect timing and consistency. Get a situation-specific estimate with the Withdrawal Risk Calculator or the broader Contraceptive Risk Calculator.
How long can sperm live in the body?
In fertile cervical mucus, sperm can survive up to 5 days, which is why intercourse several days before ovulation can still lead to pregnancy. Outside the body, sperm die quickly. To see how timing affects your odds, try the Ovulation Calculator or the One-Time Pregnancy Calculator.
Can I use this if my cycles are irregular?
Yes - this calculator doesn’t require cycle dates. For a cycle-aware fertile window, try the Ovulation Calculator.
Does breastfeeding change my chances?
It can if you meet strict LAM criteria. Check today’s status with the LAM Eligibility and Risk Calculator or explore timing with the Postpartum Ovulation Calculator.

Medical disclaimer

The information and calculators on this site are educational tools only. They provide statistical estimates based on published research and the details you enter.

They cannot diagnose, predict what will happen for you, or replace personalized advice from a licensed health care professional who knows your full history. Always talk with your doctor, midwife, or other qualified clinician before making decisions about your health, fertility, or pregnancy.

Never ignore, avoid, or delay seeking professional medical advice because of something you read here or a result you see in a calculator. If you think you may be having a medical emergency, call 911 in the United States or your local emergency number.