On Ovulation Day
1 Day Before Ovulation
2 Days Before Ovulation
3 Days Before Ovulation
4 Days Before Ovulation
5 Days Before Ovulation
1 Day After Ovulation
2 Days After Ovulation
Understanding Pregnancy Likelihood
This calculator provides an estimated likelihood of pregnancy based on several key factors related to the menstrual cycle and sexual activity. It is important to understand that this is an estimation and not a definitive diagnosis or guarantee. Individual fertility can vary significantly.
How it Works:
Pregnancy can only occur during a specific window within a woman's menstrual cycle, known as the "fertile window." This window includes the days leading up to and including ovulation. Sperm can survive in the female reproductive tract for up to 5 days, while the egg is viable for only about 12-24 hours after ovulation.
Key Factors Considered:
Days Since Ovulation: This helps establish the current phase of the cycle. Being further past ovulation generally reduces the chance of conception from recent acts.
Average Cycle Length: This is used to estimate the typical timing of ovulation, which usually occurs about 14 days before the start of the next period.
Number of Unprotected Sex Acts: More instances of unprotected intercourse increase the cumulative probability of conception, especially when timed correctly.
Timing Relative to Ovulation: The likelihood of pregnancy is highest when intercourse occurs in the 5 days leading up to ovulation and on the day of ovulation itself. Intercourse occurring after ovulation has a much lower chance of resulting in pregnancy.
The Calculation (Simplified Model: Based on average sperm/egg viability and typical fertility rates):
The underlying logic of this calculator is a simplified model that assigns a higher "probability factor" to sex acts occurring within the fertile window (roughly 5 days before ovulation to ovulation day). The probability factor decreases significantly for acts occurring after ovulation. The total likelihood is influenced by the number of sex acts and their timing, aiming to represent a cumulative chance. This model is a heuristic and not derived from a precise statistical formula applied to all individuals.
Disclaimer: This calculator is for informational purposes only and does not constitute medical advice. If you have concerns about pregnancy or fertility, please consult with a healthcare professional.
function calculateLikelihood() {
var daysSinceOvulation = parseFloat(document.getElementById("daysSinceOvulation").value);
var cycleLength = parseFloat(document.getElementById("cycleLength").value);
var sexActs = parseFloat(document.getElementById("sexActs").value);
var ovulationTiming = parseInt(document.getElementById("ovulationTiming").value);
var resultElement = document.getElementById("result");
resultElement.textContent = ""; // Clear previous result
// — Input Validation —
if (isNaN(daysSinceOvulation) || isNaN(cycleLength) || isNaN(sexActs)) {
resultElement.textContent = "Please enter valid numbers for all fields.";
return;
}
if (cycleLength 40) {
resultElement.textContent = "Cycle length should be between 20 and 40 days.";
return;
}
if (daysSinceOvulation 40) {
resultElement.textContent = "Days since ovulation should be between 0 and 40.";
return;
}
if (sexActs 0, -1 -> 1, -2 -> 2 etc.
var likelihood = 0;
if (sexActs > 0) {
var probabilityPerAct = baseFertilityFactor; // Start with a low baseline
// Adjust probability based on timing relative to ovulation
if (ovulationTiming === 0) { // On ovulation day
probabilityPerAct = maxFertilityChance;
} else if (ovulationTiming = -5) { // Days before ovulation
var daysBefore = Math.abs(ovulationTiming);
if (daysBefore 0) { // Days after ovulation
// Egg is viable for ~1 day. Minimal chance after that.
if (ovulationTiming === 1) { // 1 day after ovulation
probabilityPerAct = 0.02; // Very low chance
} else {
probabilityPerAct = 0.00; // Essentially zero chance after 1 day post-ovulation
}
}
// Cap probability to avoid exceeding 100%
probabilityPerAct = Math.min(probabilityPerAct, 1.0);
// Calculate cumulative likelihood. For simplicity, we'll sum probabilities for each act,
// capped by a maximum plausible fertility rate, rather than a complex probability multiplication.
// A more accurate model would use P(A or B) = P(A) + P(B) – P(A)*P(B), but summing up works as an estimate.
likelihood = Math.min(sexActs * probabilityPerAct, 0.95); // Cap total likelihood to 95%
likelihood = Math.max(likelihood, baseFertilityFactor); // Ensure it's at least the baseline if sex acts occurred.
} else {
likelihood = 0; // No sex acts, no likelihood.
}
// Convert likelihood to percentage string
var percentage = (likelihood * 100).toFixed(2);
resultElement.textContent = percentage + "% Likelihood";
}