Estimate your baby's estimated fetal weight (EFW) based on gestational age and common ultrasound measurements.
Enter the gestational age in weeks (e.g., 28 for 28 weeks).
Enter the BPD measurement in centimeters (cm).
Enter the HC measurement in centimeters (cm).
Enter the AC measurement in centimeters (cm).
Enter the FL measurement in centimeters (cm).
Estimated Fetal Weight (EFW)
—
Gestational Age: — weeks
Estimated Percentile: –%
EFW (grams): — g
The EFW is calculated using established sonographic formulas, most commonly the Hadlock formula, which considers BPD, HC, AC, and FL measurements. Percentile is determined by comparing the EFW to normative data for the given gestational age.
Key Assumptions: Measurements are accurate, fetus is growing typically for gestational age, and standard growth charts are applicable.
Fetal Growth Chart Data
Chart Legend:Estimated Fetal Weight (EFW) | Average Growth Curve
Typical Fetal Weight by Gestational Age (Approximation)
Gestational Age (Weeks)
Average Weight (g)
EFW Range (Lower 10th Percentile, g)
EFW Range (Upper 90th Percentile, g)
20
300
200
400
22
450
300
600
24
650
450
850
26
850
600
1100
28
1050
750
1400
30
1300
950
1700
32
1550
1150
2000
34
1850
1400
2400
36
2150
1700
2800
38
2450
2000
3200
40
2750
2300
3600
var chartInstance = null; // Global variable to hold chart instance
function validateInput(id, errorId, min, max, isDecimal) {
var input = document.getElementById(id);
var errorElement = document.getElementById(errorId);
var value = parseFloat(input.value);
var isValid = true;
errorElement.style.display = 'none';
input.style.borderColor = 'var(–border-color)';
if (input.value.trim() === ") {
errorElement.innerText = 'This field cannot be empty.';
errorElement.style.display = 'block';
input.style.borderColor = '#dc3545';
isValid = false;
} else if (isNaN(value)) {
errorElement.innerText = 'Please enter a valid number.';
errorElement.style.display = 'block';
input.style.borderColor = '#dc3545';
isValid = false;
} else if (value < 0) {
errorElement.innerText = 'Value cannot be negative.';
errorElement.style.display = 'block';
input.style.borderColor = '#dc3545';
isValid = false;
} else if (min !== null && value max) {
errorElement.innerText = 'Value is too high. Maximum is ' + max + (isDecimal ? " : ' units') + '.';
errorElement.style.display = 'block';
input.style.borderColor = '#dc3545';
isValid = false;
}
return isValid;
}
function calculateFetalWeight() {
var gestationalAge = document.getElementById('gestationalAge');
var biparietalDiameter = document.getElementById('biparietalDiameter');
var headCircumference = document.getElementById('headCircumference');
var abdominalCircumference = document.getElementById('abdominalCircumference');
var femurLength = document.getElementById('femurLength');
var gaError = document.getElementById('gestationalAgeError');
var bpdError = document.getElementById('biparietalDiameterError');
var hcError = document.getElementById('headCircumferenceError');
var acError = document.getElementById('abdominalCircumferenceError');
var flError = document.getElementById('femurLengthError');
var gaValid = validateInput('gestationalAge', 'gestationalAgeError', 0, 100, false); // Weeks
var bpdValid = validateInput('biparietalDiameter', 'biparietalDiameterError', 0, 20, true); // cm
var hcValid = validateInput('headCircumference', 'headCircumferenceError', 0, 100, true); // cm
var acValid = validateInput('abdominalCircumference', 'abdominalCircumferenceError', 0, 100, true); // cm
var flValid = validateInput('femurLength', 'femurLengthError', 0, 15, true); // cm
if (!gaValid || !bpdValid || !hcValid || !acValid || !flValid) {
document.getElementById('results').style.display = 'none';
return;
}
var ga = parseFloat(gestationalAge.value);
var bpd = parseFloat(biparietalDiameter.value);
var hc = parseFloat(headCircumference.value);
var ac = parseFloat(abdominalCircumference.value);
var fl = parseFloat(femurLength.value);
// Approximate Hadlock formula (common iteration)
// EFW = exp(1.3596 – 0.0234*AC + 0.0317*FL + 0.0428*HC + 0.158*BPD)
var efwGrams = Math.exp(1.3596 – 0.0234 * ac + 0.0317 * fl + 0.0428 * hc + 0.158 * bpd);
efwGrams = Math.round(efwGrams);
var efwKg = (efwGrams / 1000).toFixed(2);
// Simplified percentile approximation (for illustration – real charts are complex)
// This is a VERY ROUGH estimation. Actual percentiles require lookup tables.
var percentile = 50; // Default to 50th
if (ga >= 20 && ga = 0 && weekIndex < avgWeights.length) {
var referenceWeight = avgWeights[weekIndex];
if (efwGrams referenceWeight * 1.3) { // Very rough estimation for higher percentile
percentile = Math.min(95, 50 + Math.floor(((efwGrams – referenceWeight) / referenceWeight) * 50));
} else {
percentile = 50 + Math.floor(((efwGrams – referenceWeight) / referenceWeight) * 40); // Wider spread around average
percentile = Math.max(20, Math.min(80, percentile)); // Cap typical range
}
}
// Ensure percentile is within bounds
percentile = Math.max(1, Math.min(99, percentile));
}
document.getElementById('mainResult').innerText = efwKg + ' kg (' + efwGrams + ' g)';
document.getElementById('gestationalAgeResult').innerHTML = 'Gestational Age: ' + ga + ' weeks';
document.getElementById('percentileResult').innerText = percentile + '%';
document.getElementById('weightGramResult').innerText = 'EFW (grams): ' + efwGrams + ' g';
document.getElementById('results').style.display = 'block';
updateChart(ga, efwGrams, percentile);
}
function resetCalculator() {
document.getElementById('gestationalAge').value = '30';
document.getElementById('biparietalDiameter').value = '7.8';
document.getElementById('headCircumference').value = '27.0';
document.getElementById('abdominalCircumference').value = '26.0';
document.getElementById('femurLength').value = '5.8';
// Clear errors
document.getElementById('gestationalAgeError').style.display = 'none';
document.getElementById('biparietalDiameterError').style.display = 'none';
document.getElementById('headCircumferenceError').style.display = 'none';
document.getElementById('abdominalCircumferenceError').style.display = 'none';
document.getElementById('femurLengthError').style.display = 'none';
document.getElementById('results').style.display = 'none';
// Reset chart to initial state or clear dynamic data
if (chartInstance) {
chartInstance.data.datasets[0].data = []; // Clear EFW line
chartInstance.update();
}
}
function copyResults() {
var mainResult = document.getElementById('mainResult').innerText;
var gestationalAgeResult = document.getElementById('gestationalAgeResult').innerText.replace('Gestational Age: ', ");
var percentileResult = document.getElementById('percentileResult').innerText.replace('Estimated Percentile: ', ");
var weightGramResult = document.getElementById('weightGramResult').innerText.replace('EFW (grams): ', ");
var assumptions = document.querySelectorAll('.key-assumptions strong')[0].nextSibling.textContent.trim();
var textToCopy = "Estimated Fetal Weight Calculation:\n\n" +
mainResult + "\n" +
gestationalAgeResult + "\n" +
percentileResult + "\n" +
weightGramResult + "\n\n" +
"Key Assumptions: " + assumptions;
navigator.clipboard.writeText(textToCopy).then(function() {
// Optionally provide user feedback
var copyButton = document.querySelector('button.copy');
var originalText = copyButton.innerText;
copyButton.innerText = 'Copied!';
setTimeout(function() {
copyButton.innerText = originalText;
}, 2000);
}).catch(function(err) {
console.error('Failed to copy text: ', err);
alert('Failed to copy results. Please copy manually.');
});
}
// Charting Functions
function updateChart(currentGA, currentEFW, currentPercentile) {
var ctx = document.getElementById('fetalGrowthChart').getContext('2d');
// Static data for average growth curve (approximate)
var averageWeeks = [20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40];
var averageWeights = [300, 450, 650, 850, 1050, 1300, 1550, 1850, 2150, 2450, 2750]; // in grams
// Data for the estimated fetal weight point
var efwData = [];
if (currentGA >= 20 && currentGA <= 40) {
efwData.push({ x: currentGA, y: currentEFW });
}
// Data for percentile ranges (approximate)
var lowerPercentileWeights = [200, 300, 450, 600, 750, 950, 1150, 1400, 1700, 2000, 2300]; // 10th percentile approx
var upperPercentileWeights = [400, 600, 850, 1100, 1400, 1700, 2000, 2400, 2800, 3200, 3600]; // 90th percentile approx
if (chartInstance) {
chartInstance.data.datasets[0].data = efwData; // EFW point
chartInstance.data.datasets[1].data = averageWeeks.map(function(week, index) { return { x: week, y: averageWeights[index] }; }); // Average curve
chartInstance.data.datasets[2].data = averageWeeks.map(function(week, index) { return { x: week, y: lowerPercentileWeights[index] }; }); // Lower percentile
chartInstance.data.datasets[3].data = averageWeeks.map(function(week, index) { return { x: week, y: upperPercentileWeights[index] }; }); // Upper percentile
chartInstance.update();
} else {
chartInstance = new Chart(ctx, {
type: 'scatter', // Use scatter to plot points and lines accurately
data: {
datasets: [{
label: 'Estimated Fetal Weight (EFW)',
data: efwData, // Current EFW point
backgroundColor: 'var(–primary-color)',
borderColor: 'var(–primary-color)',
pointRadius: 8,
pointHoverRadius: 10,
borderWidth: 2,
type: 'scatter' // Specify type for scatter points
},
{
label: 'Average Growth Curve (10-40 Weeks)',
data: averageWeeks.map(function(week, index) { return { x: week, y: averageWeights[index] }; }),
borderColor: 'var(–success-color)',
backgroundColor: 'var(–success-color)',
fill: false,
tension: 0.1,
type: 'line' // Specify type for line chart
},
{
label: '10th Percentile Range',
data: averageWeeks.map(function(week, index) { return { x: week, y: lowerPercentileWeights[index] }; }),
borderColor: 'rgba(0, 74, 153, 0.3)',
backgroundColor: 'rgba(0, 74, 153, 0.1)',
fill: false,
tension: 0.1,
type: 'line'
},
{
label: '90th Percentile Range',
data: averageWeeks.map(function(week, index) { return { x: week, y: upperPercentileWeights[index] }; }),
borderColor: 'rgba(40, 167, 69, 0.3)',
backgroundColor: 'rgba(40, 167, 69, 0.1)',
fill: '+1', // Fills to the dataset defined above it (90th percentile fill area)
tension: 0.1,
type: 'line'
}]
},
options: {
responsive: true,
maintainAspectRatio: false,
scales: {
x: {
type: 'linear',
position: 'bottom',
title: {
display: true,
text: 'Gestational Age (Weeks)'
},
min: 18,
max: 42,
ticks: {
stepSize: 2
}
},
y: {
title: {
display: true,
text: 'Weight (grams)'
},
min: 0,
max: 4000, // Adjust max as needed
ticks: {
callback: function(value, index, values) {
return value + ' g';
}
}
}
},
plugins: {
title: {
display: true,
text: 'Estimated Fetal Weight Growth Chart',
font: { size: 16 }
},
legend: {
display: false // Legend is handled by custom text for clarity
},
tooltip: {
callbacks: {
label: function(context) {
var label = context.dataset.label || '';
if (label) {
label += ': ';
}
if (context.parsed.y !== null) {
label += context.parsed.y.toFixed(0) + ' g';
}
if (context.dataset.type === 'scatter' && context.parsed.x !== null) {
label += ' (GA: ' + context.parsed.x.toFixed(0) + ' weeks)';
}
return label;
}
}
}
}
}
});
}
}
// Initialize chart on load with default state
window.onload = function() {
updateChart(0, 0, 0); // Initialize with empty data
// Add functionality for FAQ toggles
var faqQuestions = document.querySelectorAll('.faq-question');
faqQuestions.forEach(function(question) {
question.addEventListener('click', function() {
var answer = this.nextElementSibling;
this.classList.toggle('active');
if (answer.style.display === 'block') {
answer.style.display = 'none';
} else {
answer.style.display = 'block';
}
});
});
// Set default values for the calculator
resetCalculator();
};