No / Used Protection
Yes, Once
Yes, Multiple Times
Not sure / Protection Failure
Based on your inputs, your estimated probability of pregnancy is:
0%
Disclaimer: This calculator is for educational and informational purposes only. It is not a medical diagnosis. The only way to confirm pregnancy is through a clinical pregnancy test (urine or blood) or an ultrasound.
How the Pregnancy Percentage Calculator Works
Determining the likelihood of pregnancy involves looking at two main factors: biological timing and physiological symptoms. This calculator analyzes the dates of your menstrual cycle alongside common early pregnancy symptoms caused by the hormone hCG (human Chorionic Gonadotropin).
The calculation assigns weights to various factors. For instance, a missed period is the most significant indicator, while symptoms like nausea or breast tenderness add to the cumulative probability. If you have had unprotected intercourse during your fertile window (ovulation), the mathematical probability increases significantly.
Common Early Pregnancy Symptoms
Symptom
Typical Timing
Why it Happens
Missed Period
4 weeks after last period
Progesterone remains high to support the uterine lining.
Implantation Bleeding
6-12 days after conception
The embryo attaches to the uterine wall, causing light spotting.
Tender Breasts
1-2 weeks after conception
Hormonal surges increase blood flow and change breast tissue.
Nausea
2-8 weeks after conception
Rapidly rising levels of hCG and estrogen.
When Should You Take a Pregnancy Test?
While this calculator provides a percentage based on statistical symptoms, the timing of a physical test is crucial for accuracy. Most home pregnancy tests are designed to detect hCG once it reaches a certain threshold in your urine.
Before a Missed Period: Some "early result" tests can detect pregnancy 4-5 days before your expected period, but the chance of a false negative is higher.
After a Missed Period: Waiting until the first day of your missed period provides roughly 99% accuracy for most over-the-counter tests.
Time of Day: Testing with your first morning urine provides the highest concentration of hCG.
Understanding the Fertile Window
A typical menstrual cycle is 28 days. Ovulation generally occurs around day 14. Because sperm can live inside the female reproductive tract for up to 5 days and the egg lives for 12-24 hours, the "fertile window" is approximately 6 days long. If you had unprotected sex during this window, the percentage likelihood of conception is at its peak.
function calculatePregnancy() {
var daysSinceLast = parseFloat(document.getElementById('daysSinceLastPeriod').value);
var cycleLength = parseFloat(document.getElementById('cycleLength').value);
var sexFactor = parseFloat(document.getElementById('unprotectedSex').value);
var symptoms = document.getElementsByClassName('symptom');
if (isNaN(daysSinceLast) || isNaN(cycleLength)) {
alert("Please enter valid numbers for your cycle dates.");
return;
}
var percentage = 0;
// 1. Timing Logic (Missed Period)
if (daysSinceLast > cycleLength) {
var daysLate = daysSinceLast – cycleLength;
if (daysLate > 0 && daysLate 7) {
percentage += 60;
}
} else if (daysSinceLast > (cycleLength – 3)) {
// Approaching period
percentage += 10;
}
// 2. Intercourse Logic
if (sexFactor === 1) {
percentage += 20;
} else if (sexFactor === 2) {
percentage += 35;
} else if (sexFactor === 0.5) {
percentage += 10;
}
// 3. Symptom Logic
for (var i = 0; i < symptoms.length; i++) {
if (symptoms[i].checked) {
percentage += parseFloat(symptoms[i].value);
}
}
// 4. Base Probability Cap
// If no sex factor and no late period, but symptoms exist
if (sexFactor === 0 && daysSinceLast 99) percentage = 99;
if (percentage 0 || daysSinceLast > cycleLength)) percentage = 5;
if (percentage < 1) percentage = 1;
// Display Result
var resultDiv = document.getElementById('pregnancyResult');
var scoreDisplay = document.getElementById('scoreDisplay');
var adviceText = document.getElementById('adviceText');
resultDiv.style.display = 'block';
scoreDisplay.innerHTML = Math.round(percentage) + "%";
var advice = "";
if (percentage < 25) {
advice = "Your probability is low. Symptoms may be related to your upcoming period (PMS). If your period is late, wait 2-3 days and test.";
resultDiv.style.backgroundColor = "#f1f8e9";
} else if (percentage < 60) {
advice = "There is a moderate chance. Many of these symptoms overlap with early pregnancy. It is recommended to take a home pregnancy test tomorrow morning.";
resultDiv.style.backgroundColor = "#fff3e0";
} else {
advice = "Your probability is high based on your symptoms and cycle timing. You should take a pregnancy test as soon as possible and consult with a healthcare professional.";
resultDiv.style.backgroundColor = "#fce4ec";
}
adviceText.innerHTML = advice;
// Smooth scroll to result
resultDiv.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}