Pregnancy Chance Calculator

Get an instant, rough estimate. Results are educational — not medical advice.

This tool provides estimates only and is not medical advice.

Want a more precise estimate?

Try the Advanced Calculator »

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How to Use This Calculator

  1. Choose a contraceptive method (optional) — leave as “No contraceptive” if none was used.
  2. Enter the number of intercourse events you want to estimate for (any time frame).
    Only one event? Use our One-Time Pregnancy Chance Calculator.
  3. Enter your age (optional) and tap Calculate.

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

How the Estimate Is Calculated (The Science)

We begin with a per-act probability of conception that reflects your selected method’s real-world (typical-use) effectiveness and age-related fertility. For multiple acts, we combine the probabilities across the window you chose. Extremely small and large values are displayed as “Under 0.001%” or “Over 99.999%” for clarity.

Want more control (BMI, lifestyle, and timing scenarios)? Try the Advanced Calculator.

The Key Factors in Our Model

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Female Age

Primary driver of fertility. We follow recognized guidance on age-related decline in ovarian reserve and egg quality (ACOG overview).

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Male Age

Paternal age influences sperm quality; effects are clearer beyond 40 (PubMed: paternal age).

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Intercourse Timing

Odds peak in the 5-day fertile window and ovulation day. Frequency across the window can outperform exact targeting (frequency vs. timing). Try our Ovulation Calculator.

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Body Mass Index (BMI)

Very low or high BMI can disrupt ovulation; our advanced model adjusts accordingly (BMI & fertility). Explore the Advanced Calculator.

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Lifestyle

Smoking and heavy alcohol intake can reduce fertility via hormonal pathways (evidence summary). See personalized tips after your result.

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Contraceptive Use

We use large-scale typical-use data (e.g., Trussell 2011) to estimate method-specific risk. Compare methods in our Contraceptive Risk Calculator.

Data Sources & Primary Research

See our full Research Library for methods, assumptions, and additional datasets.

Medical Disclaimer

This calculator is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified clinician about contraception, fertility, or pregnancy concerns.

Frequently asked questions

How many days after my period can I get pregnant?
The fertile window typically spans cycle days 10–15 in a 28-day cycle, with ovulation around day 14. Shorter/longer cycles shift this window. For a personalized window, try our Ovulation Calculator.
Is there ever a 100% chance of pregnancy?
No. 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. See your most fertile days with the Ovulation Calculator.
How can I be sure I ovulated?
Confirmation is retrospective (e.g., sustained basal temperature rise) or via ultrasound. OPKs show LH surge but don’t prove ovulation alone. For help, try our BBT Ovulation Calculator and OPK → Ovulation Timing Calculator.
How reliable is the withdrawal (pull-out) method?
Typical-use effectiveness is ~78% annually. For situation-specific estimates, see our Withdrawal Risk Calculator or compare methods in the Contraceptive Risk Calculator.
How long can sperm live in the body?
Up to 5 days in fertile cervical mucus. That’s why sex several days before ovulation can still lead to pregnancy. Explore timing with the Ovulation Calculator or get a single-event estimate in the One-Time Calculator.
What if I used emergency contraception (Plan B or Ella)?
EC can lower your chances depending on the pill type and timing. See our Morning-After Pill Effectiveness Calculator.
Does breastfeeding (LAM) change my chances?
LAM can suppress ovulation if strict criteria are met. Check status with the LAM Eligibility & Risk Calculator or explore timing using the Postpartum Ovulation Calculator.