Pregnancy Chance Estimator | Calendar-Based Estimate

This tool estimates the likelihood of pregnancy based on the timing of intercourse relative to your estimated ovulation date. It provides a general category only — no percentages. This is a calendar-based estimate and cannot confirm or rule out pregnancy.

First day of last menstrual period

Average cycle length (days)

Most cycles are 28 days. Usual range is 21–45 days.

Your cycle length is outside the usual range for this calculator. Please consult a healthcare professional if your cycles are very irregular.

Date of intercourse

Was contraception used?

This tool cannot accurately estimate pregnancy chance when contraception was used. The effectiveness of contraception depends on the method, how it was used, and individual factors. Please consult a healthcare professional if you have concerns.

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Pregnancy Chance Estimate

Calendar-based estimate only — not a medical prediction

Estimated ovulation date

Days from intercourse to ovulation

Fertile window estimate

🧪 When to take a pregnancy test A home urine pregnancy test is most reliable from the first day of a missed period — typically at least 14 days after the date of intercourse. Testing too early may give a false negative result. If your period is more than a week late, consult a doctor.

⚠️ This is an estimate, not a medical result Actual pregnancy chance depends on many individual factors including age, health, fertility, sperm quality, and how regular your cycle is. This tool does not account for those factors. A calendar estimate cannot confirm or rule out pregnancy.

How Timing Affects Pregnancy Chance

Pregnancy can only occur if sperm fertilises an egg. The egg survives for approximately 12–24 hours after ovulation. Sperm can survive in the reproductive tract for up to about 5 days. This means the period around ovulation — particularly the 1–2 days before and the day of ovulation — carries the highest chance of conception.

What the Categories Mean

Higher chance — Intercourse occurred 1–2 days before or on the estimated ovulation day. This is the highest-chance window based on calendar timing.

Moderate chance — Intercourse occurred 3–5 days before ovulation or 1 day after. Sperm may still be viable, or the egg may have just been released.

Low chance — Intercourse occurred 6–7 days before ovulation or 2 days after. Sperm survival and egg viability make conception less likely but not impossible.

Very low chance — Intercourse was well outside the likely fertile window. Pregnancy is unlikely but cannot be completely excluded due to cycle variation.

Limitations of Calendar Estimates

This tool assumes ovulation occurs 14 days before the next expected period. In reality, ovulation timing varies from cycle to cycle and from person to person. Stress, illness, hormonal changes, irregular periods, PCOS, thyroid conditions, and other factors can all shift ovulation. A calendar estimate cannot account for these individual differences.

When to Take a Pregnancy Test

Home urine pregnancy tests detect the hormone hCG, which rises after a fertilised egg implants. Testing is most reliable from the first day of a missed period — usually at least 14 days after intercourse. Early testing may give a false negative result because hCG levels may not yet be high enough to detect. If you receive a negative result but your period does not arrive, test again a few days later. A positive result should be confirmed with a doctor.

Related Fertility Tools

Frequently Asked Questions

This is a calendar-based educational estimate only. It cannot confirm or rule out pregnancy. Actual pregnancy chance depends on many individual factors including age, health, fertility, and cycle regularity.

A home urine pregnancy test is most reliable from the first day of a missed period, usually at least 14 days after intercourse. Testing too early may give a false negative result.

Pregnancy is most likely around ovulation, but ovulation timing can vary. Sperm can survive several days. No day in a cycle can be guaranteed as completely safe.

Take a home pregnancy test from the first day of a missed period. If positive, or if your period is more than a week late, consult a doctor.