Baby Weight Percentile Calculator Weeks Australia

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Baby Weight Percentile Calculator

What is a Baby Weight Percentile Calculator (Weeks) – Australia?

A Baby Weight Percentile Calculator (Weeks) for Australia is a specialised online tool designed to help parents, caregivers, and healthcare professionals assess a baby’s growth. It specifically measures a baby’s weight in relation to their age in weeks and compares it against established growth charts for the Australian population. This comparison is expressed as a percentile, providing a standardised way to understand if a baby is growing at a healthy pace relative to their peers. In Australia, these calculators typically reference data aligned with international standards like the World Health Organization (WHO) growth charts, often with considerations for local demographic data.

Who should use it?
Primarily, parents and guardians of infants up to one year old can use this calculator to gain insights into their baby’s growth trajectory between regular paediatrician visits. It’s also a valuable tool for midwives, child health nurses, and doctors to quickly screen and monitor infant development. Midwives in Australia frequently use such tools to provide reassurance or identify potential concerns early.

Common Misconceptions:
A common misunderstanding is that a low percentile (e.g., below the 10th) automatically signifies a problem. However, babies naturally fall along a spectrum of growth. A consistently tracking baby along a specific percentile curve is often more important than the exact percentile number itself. Conversely, a high percentile doesn’t always mean the baby is overweight, especially in the early months. It’s crucial to interpret the results within the context of the baby’s overall health, feeding, and development. Consulting a healthcare professional is always recommended for definitive advice regarding baby weight percentile calculator weeks australia.

Baby Weight Percentile Calculator (Weeks) – Australia Formula and Mathematical Explanation

The calculation of baby weight percentiles is not a simple linear formula. It relies on complex statistical models derived from large datasets of infant growth. Australian growth charts, largely based on WHO standards, use the LMS (Lambda-Mu-Sigma) method. This method models the 3rd, 50th (median), and 97th percentiles, along with measures of variability (LMS values) at each age point.

The Process:
1. **Data Input:** The calculator takes the baby’s age in weeks, weight in kilograms, and sex as input.
2. Lookup: It references a comprehensive dataset (or a statistical model derived from it) that contains the LMS values for each week of age, separately for boys and girls.
3. Z-score Calculation: Using the baby’s weight (W), the corresponding age’s median (M), coefficient of variation (S), and skewness index (L) from the reference data, a Z-score is calculated. The formula is approximately:
Z = { [ (W/M)^L – 1 ] / (L*S) }
*Note: If L=0, the formula is approximated using logarithms.*
4. Percentile Conversion: The calculated Z-score is then converted into a percentile using the standard normal distribution function (also known as the cumulative distribution function or CDF). This function P(Z) gives the probability that a randomly selected baby from the reference population will have a Z-score less than or equal to Z. This probability is then multiplied by 100 to get the percentile rank.

The calculator also determines the *Weight for Age* (which is simply the baby’s entered weight) and compares it to the *Median Weight* (50th percentile) for that specific age and sex from the growth chart data. The *Difference from Average* is the baby’s weight minus the median weight.

Variables Table:

Key Variables and Their Meanings

Variable	Meaning	Unit	Typical Range (for context)
Age (Weeks)	Baby’s age measured in completed weeks since birth.	Weeks	0 – 52 weeks
Weight (kg)	Baby’s current body mass.	Kilograms (kg)	0.5 kg – 15 kg (approx. for 0-1 year)
Sex	Biological sex of the infant (Male/Female).	Categorical	Male, Female
LMS Values	Parameters (Lambda, Mu, Sigma) describing the shape of the distribution at a specific age.	Statistical values	Varies by age and sex
Z-score	Number of standard deviations a baby’s weight is from the median weight for their age and sex.	Unitless	Typically -3 to +3 (can extend)
Percentile	The percentage of babies of the same age and sex whose weight is less than or equal to the baby’s weight.	%	0 – 100%
Median Weight	The weight at the 50th percentile for a given age and sex.	Kilograms (kg)	Varies significantly by age and sex

Practical Examples (Real-World Use Cases)

Understanding the baby weight percentile calculator weeks australia involves seeing it in action. Here are two practical examples:

Example 1: A Growing Boy

Scenario: Sarah’s son, Leo, is 10 weeks old. He weighs 6.8 kg and is a boy. Sarah is curious about how his weight compares to other 10-week-old boys in Australia.

Inputs:

• Age: 10 weeks
• Weight: 6.8 kg
• Sex: Male

Calculator Output:

• Main Result: 75th Percentile
• Weight for Age: 6.8 kg
• Average Weight (for age/sex): 7.1 kg
• Difference from Average: -0.3 kg

Interpretation: Leo’s weight of 6.8 kg places him at the 75th percentile for a 10-week-old boy in Australia. This means he weighs more than 75% of baby boys his age and less than 25%. He is slightly lighter than the average weight (50th percentile) for his age, which is 7.1 kg, by 0.3 kg. This is a healthy growth pattern, indicating he is well-fed and developing appropriately within the upper range of normal growth.

Example 2: A Petite Girl

Scenario: Mark and Emily’s daughter, Chloe, is 24 weeks old (6 months). She weighs 7.2 kg and is a girl. They want to check her weight percentile.

Inputs:

• Age: 24 weeks
• Weight: 7.2 kg
• Sex: Female

Calculator Output:

• Main Result: 20th Percentile
• Weight for Age: 7.2 kg
• Average Weight (for age/sex): 8.1 kg
• Difference from Average: -0.9 kg

Interpretation: Chloe’s weight of 7.2 kg puts her at the 20th percentile for a 24-week-old girl in Australia. This indicates that 20% of baby girls her age weigh the same or less than Chloe. She is lighter than the average weight (50th percentile) for her age, which is 8.1 kg, by 0.9 kg. This is also considered a normal and healthy growth pattern. Many babies track consistently on percentiles below the 50th, and as long as Chloe is meeting developmental milestones, feeding well, and gaining weight steadily, there is likely no cause for concern. It’s always best to discuss these results with a paediatrician.

How to Use This Baby Weight Percentile Calculator (Weeks) – Australia

Using the baby weight percentile calculator weeks australia is straightforward. Follow these steps for accurate results:

1. Accurate Age: Ensure you enter the baby’s age in completed weeks. For example, if the baby is 3 months and 2 weeks old, that’s approximately 14 weeks (3 months * ~4.3 weeks/month + 2 weeks). Double-check your calculation of weeks.
2. Precise Weight: Weigh your baby on a calibrated infant scale if possible. Enter the weight in kilograms (e.g., 5.5 kg, not 5500g or 12.1 lbs). Consistency in measurement is key.
3. Correct Sex: Select the correct sex (Male or Female) as the growth charts differ significantly between sexes.
4. Calculate: Click the “Calculate Percentile” button. The results will update instantly.
5. Interpret Results:
   • Main Result (Percentile): This is the most important figure. It tells you where your baby sits relative to others of the same age and sex. A percentile between the 3rd and 97th is generally considered within the normal range.
   • Weight for Age: This is simply your baby’s entered weight.
   • Average Weight: This is the weight at the 50th percentile for your baby’s age and sex.
   • Difference from Average: This shows how many kilograms your baby’s weight deviates from the 50th percentile.
6. Decision-Making Guidance:
   • Stable Growth: If your baby’s percentile remains relatively consistent over time (e.g., always around the 60th percentile), this indicates steady, healthy growth, even if it’s not near the 50th.
   • Significant Jumps/Drops: A sudden, large shift up or down in percentile (e.g., from 50th to 10th, or 20th to 90th) over a short period warrants a discussion with your paediatrician.
   • Concern: If your baby is consistently below the 3rd percentile or above the 97th percentile, or if you have any concerns about their feeding, energy levels, or development, consult your healthcare provider immediately. This calculator is an informational tool, not a substitute for professional medical advice.
7. Reset/Copy: Use the “Reset” button to clear fields and start over. Use “Copy Results” to save the calculated data for your records or to share with your doctor.

Key Factors That Affect Baby Weight Percentile Results

While the calculator provides a numerical output, several underlying factors influence a baby’s weight and, consequently, their percentile. Understanding these helps in interpreting the results more holistically:

• Genetics: Just like adults, babies inherit genetic predispositions for body size and frame. A baby born to larger parents might naturally trend towards higher percentiles, while a baby from smaller parents might trend lower. This is a primary factor in a baby weight percentile calculator weeks australia.
• Feeding Method & Volume: Whether a baby is breastfed or formula-fed can influence weight gain patterns. Breastfed babies sometimes show slower weight gain in the second half of the first year compared to formula-fed babies, but this is usually normal. The adequacy of milk intake (frequency, duration, or volume) is critical. Ensure the baby is effectively latching or receiving sufficient formula.
• Maternal Health & Nutrition During Pregnancy: The mother’s diet, weight gain during pregnancy, and overall health (e.g., gestational diabetes) can impact fetal growth and birth weight, setting the initial trajectory for postnatal growth.
• Prematurity: Premature babies often have lower birth weights and may take longer to “catch up” to full-term growth curves. Growth charts for premature infants often use corrected age. This calculator is for babies born full-term or near full-term.
• Infant Health & Illness: Underlying medical conditions, chronic illnesses, digestive issues (like reflux or allergies), or frequent infections can affect appetite and nutrient absorption, leading to slower weight gain and lower percentiles.
• Activity Level: As babies become more mobile (rolling, sitting, crawling), they burn more calories. While typically not a major factor in the first few months, increased activity can influence weight gain rates later in infancy.
• Accuracy of Measurements: Inconsistent or inaccurate weighing (e.g., weighing with clothes on, using a non-calibrated scale, or measuring weight at different times of day) can lead to misleading results and affect the perceived percentile.
• Growth Spurts and Fluctuations: Infant growth is not linear. Babies experience growth spurts where they gain weight rapidly, followed by periods of slower gain. Percentiles can fluctuate slightly during these times.

Frequently Asked Questions (FAQ)

Q1: What is a ‘normal’ baby weight percentile in Australia?

A: Generally, a baby weighing between the 3rd and 97th percentile for their age and sex is considered within the normal growth range in Australia, aligning with WHO standards. The 50th percentile represents the average weight.

Q2: My baby is in the 10th percentile. Should I be worried?

A: Not necessarily. If your baby has consistently been around the 10th percentile since birth, is meeting developmental milestones, feeding well, and gaining weight steadily, it’s likely their natural growth curve. Worrying is more warranted if there’s a sudden drop in percentile or if the baby shows signs of poor feeding or developmental delays.

Q3: How often should I use the baby weight percentile calculator weeks australia?

A: It’s best to use it periodically, perhaps monthly or when you have your baby weighed, especially if you have concerns or want to track progress between paediatrician check-ups. Overuse can lead to unnecessary anxiety.

Q4: Does breastfeeding affect percentile calculations?

A: Breastfeeding can influence weight gain patterns. Some studies show breastfed babies may gain weight more slowly in the latter half of the first year compared to formula-fed babies, but they often catch up later. The calculator uses standard charts that encompass both feeding methods.

Q5: What’s the difference between weight percentile and BMI percentile?

A: This calculator focuses solely on weight percentile for age. BMI (Body Mass Index) percentile is a different metric, calculated using both weight and height, and is typically used for older children and adults to assess body fatness.

Q6: My baby was born premature. Should I use this calculator?

A: For premature babies, it’s best to use growth charts specifically designed for preterm infants, often using ‘corrected age’ (age from the due date, not the birth date). This calculator is primarily intended for babies born at term (37-40 weeks).

Q7: How are Australian growth charts different from international ones?

A: Australian growth charts are largely based on WHO international standards but may incorporate some Australian-specific data or be presented in a format most familiar to Australian healthcare providers. For practical purposes, they are very similar and aim for global consistency in assessing child growth.

Q8: What if my baby’s weight difference from average is large?

A: A large difference from the average (50th percentile) isn’t inherently bad if the baby’s growth curve is consistent. However, it’s a prompt to ensure the baby is healthy, feeding adequately, and developing normally. Always discuss significant deviations or concerns with your child health nurse or paediatrician.

Growth Data Summary

Age (Weeks)	Baby’s Weight (kg)	Median Weight (kg)	Percentile (%)
—	—	—	—

Related Tools and Internal Resources

• Baby Length and Head Circumference Calculator – Track other key growth metrics for your baby.
• Infant Feeding Guide – Tips and advice on ensuring your baby gets adequate nutrition.
• Baby Development Milestones – Understand what to expect at different stages of your baby’s growth.
• Australian Paediatric Care Guidelines – Official resources for child health in Australia.
• Newborn Weight Gain Calculator – Specific tool for tracking initial weight recovery after birth.
• Childhood Nutrition Advice – Information on healthy eating for growing children.

// — Mock Data for Growth Charts (Simplified LMS-like representation) —
// In a real-world scenario, this data would be extensive and accurate.
// For demonstration, we’ll use simplified average weights and approximate percentiles.
// Structure: { sex_index: { age_in_weeks: { median_weight_kg, percentile_points_for_chart } } }
// percentile_points_for_chart: Array of [age, percentile] pairs for plotting
var growthData = {
0: { // Male
0: {median_weight_kg: 3.3, chartPoints: [[0, 3.3], [10, 4.2], [24, 7.1], [52, 9.5]]},
10: {median_weight_kg: 4.2, chartPoints: [[0, 3.3], [10, 4.2], [24, 7.1], [52, 9.5]]},
24: {median_weight_kg: 7.1, chartPoints: [[0, 3.3], [10, 4.2], [24, 7.1], [52, 9.5]]},
52: {median_weight_kg: 9.5, chartPoints: [[0, 3.3], [10, 4.2], [24, 7.1], [52, 9.5]]}
},
1: { // Female
0: {median_weight_kg: 3.1, chartPoints: [[0, 3.1], [10, 4.0], [24, 8.1], [52, 9.0]]},
10: {median_weight_kg: 4.0, chartPoints: [[0, 3.1], [10, 4.0], [24, 8.1], [52, 9.0]]},
24: {median_weight_kg: 8.1, chartPoints: [[0, 3.1], [10, 4.0], [24, 8.1], [52, 9.0]]},
52: {median_weight_kg: 9.0, chartPoints: [[0, 3.1], [10, 4.0], [24, 8.1], [52, 9.0]]}
}
};

// Simplified approximate percentile calculation based on mock data
// In a real calculator, this would use LMS values and Z-scores.
function getApproximatePercentile(ageWeeks, weightKg, sexIndex) {
var dataForSex = growthData[sexIndex];
if (!dataForSex) return { percentile: NaN, medianWeight: NaN, weightForAge: weightKg, difference: NaN };

// Find the closest age data points
var ages = Object.keys(dataForSex).map(Number).sort(function(a, b) { return a – b; });
var lowerAge = 0, upperAge = ages[ages.length – 1];

for (var i = 0; i < ages.length; i++) {
if (ages[i] = ageWeeks) {
upperAge = ages[i];
break;
}
}

var lowerData = dataForSex[lowerAge];
var upperData = dataForSex[upperAge];

var medianWeight;
var percentile;

if (lowerAge === upperAge || ageWeeks === 0) {
medianWeight = lowerData.median_weight_kg;
} else {
// Linear interpolation for median weight
var factor = (ageWeeks – lowerAge) / (upperAge – lowerAge);
medianWeight = lowerData.median_weight_kg + factor * (upperData.median_weight_kg – lowerData.median_weight_kg);
}

// VERY simplified percentile estimation for demo chart – not a real calculation
// This part is highly simplified and doesn’t reflect true LMS methods.
// A real implementation requires statistical libraries or pre-computed tables.
var minWeight = medianWeight * 0.7; // Rough estimate for ~10th percentile
var maxWeight = medianWeight * 1.3; // Rough estimate for ~90th percentile

if (weightKg maxWeight) {
percentile = Math.min(97, 50 + Math.round(((weightKg – medianWeight) / (maxWeight – medianWeight)) * 40)); // Clamp at 97%
} else {
percentile = 50 + Math.round(((weightKg – medianWeight) / (maxWeight – medianWeight)) * 40);
}
percentile = Math.max(3, Math.min(97, percentile)); // Ensure within 3-97 range

var difference = parseFloat((weightKg – medianWeight).toFixed(2));

return { percentile: percentile, medianWeight: medianWeight, weightForAge: weightKg, difference: difference };
}

// — Charting —
var growthChart;
var chartData = {
labels: [],
datasets: [
{
label: ‘Median Weight (50th %ile)’,
data: [],
borderColor: ‘rgba(0, 74, 153, 1)’, // Primary color
backgroundColor: ‘rgba(0, 74, 153, 0.1)’,
tension: 0.1,
fill: false,
pointRadius: 5,
pointHoverRadius: 7
},
{
label: ‘Your Baby\’s Weight’,
data: [],
borderColor: ‘rgba(40, 167, 69, 1)’, // Success color
backgroundColor: ‘rgba(40, 167, 69, 0.1)’,
tension: 0.1,
fill: false,
pointRadius: 5,
pointHoverRadius: 7
}
]
};

function updateChart() {
var babyAgeWeeksInput = document.getElementById(‘babyAgeWeeks’);
var babyWeightKgInput = document.getElementById(‘babyWeightKg’);
var babySexSelect = document.getElementById(‘babySex’);

var ageWeeks = parseInt(babyAgeWeeksInput.value);
var weightKg = parseFloat(babyWeightKgInput.value);
var sexIndex = parseInt(babySexSelect.value);

// Clear previous data
chartData.labels = [];
chartData.datasets[0].data = [];
chartData.datasets[1].data = [];

// Get relevant chart points from mock data
var sexData = growthData[sexIndex];
if (sexData) {
var sortedAges = Object.keys(sexData).map(Number).sort(function(a, b) { return a – b; });

// Add median weight points for plotting
sortedAges.forEach(function(age) {
var dataPoint = sexData[age];
if (dataPoint && dataPoint.chartPoints) {
chartData.datasets[0].data.push({x: age, y: dataPoint.median_weight_kg});
chartData.labels.push(age); // Add labels based on median points
}
});

// Add baby’s weight point
if (!isNaN(ageWeeks) && !isNaN(weightKg) && ageWeeks >= 0 && weightKg > 0) {
chartData.datasets[1].data.push({x: ageWeeks, y: weightKg});
// Ensure the baby’s age is also a label if not already present
if (chartData.labels.indexOf(ageWeeks) === -1) {
chartData.labels.push(ageWeeks);
chartData.labels.sort(function(a, b) { return a – b; }); // Keep labels sorted
}
}
}

// Ensure labels array matches the number of data points for each dataset if needed,
// or use {x, y} objects which Chart.js handles well. Using {x, y} objects is cleaner.
// Update x-axis labels if needed based on the range of data points.
var minLabel = Math.min.apply(null, chartData.labels);
var maxLabel = Math.max.apply(null, chartData.labels);
if (chartData.labels.length > 0) {
chartData.labels = chartData.labels.map(function(label) {
// You might format this further, e.g., ‘Wk ‘ + label
return label;
});
} else {
chartData.labels = [‘0′, ’10’, ’24’, ’52’]; // Default labels if no data
}

// Ensure datasets have the same number of points or use {x,y} format
// Chart.js handles {x,y} data arrays well, aligning points by ‘x’ value.

if (growthChart) {
growthChart.update();
} else {
var ctx = document.getElementById(‘growthChart’).getContext(‘2d’);
// Destroy previous chart instance if it exists to prevent memory leaks
if (window.growthChartInstance) {
window.growthChartInstance.destroy();
}
window.growthChartInstance = new Chart(ctx, {
type: ‘line’,
data: chartData,
options: {
responsive: true,
maintainAspectRatio: true, // Adjust as needed
scales: {
x: {
type: ‘linear’, // Use linear scale for weeks
position: ‘bottom’,
title: {
display: true,
text: ‘Age (Weeks)’
},
ticks: {
// Auto-generate ticks or specify a stepSize
stepSize: 5 // Example: show a tick every 5 weeks
}
},
y: {
title: {
display: true,
text: ‘Weight (kg)’
},
beginAtZero: false // Weight doesn’t start at 0
}
},
plugins: {
tooltip: {
callbacks: {
label: function(context) {
var label = context.dataset.label || ”;
if (label) {
label += ‘: ‘;
}
if (context.parsed.x !== null) {
label += ‘Week ‘ + context.parsed.x + ‘, ‘;
}
if (context.parsed.y !== null) {
label += context.parsed.y.toFixed(2) + ‘ kg’;
}
return label;
}
}
},
legend: {
position: ‘top’,
}
}
}
});
growthChart = window.growthChartInstance; // Assign to the global variable
}
}

function validateInput(id, errorId, minValue, maxValue) {
var input = document.getElementById(id);
var errorSpan = document.getElementById(errorId);
var value = input.value.trim();
var isValid = true;

errorSpan.style.display = ‘none’;
input.style.borderColor = ‘#ccc’;

if (value === “”) {
errorSpan.textContent = “This field cannot be empty.”;
isValid = false;
} else {
var numValue = parseFloat(value);
if (isNaN(numValue)) {
errorSpan.textContent = “Please enter a valid number.”;
isValid = false;
} else {
if (minValue !== undefined && numValue maxValue) {
errorSpan.textContent = “Value cannot be greater than ” + maxValue + “.”;
isValid = false;
}
if (numValue < 0) { // Specific check for negative numbers
errorSpan.textContent = "Value cannot be negative.";
isValid = false;
}
}
}

if (isValid) {
input.style.borderColor = '#28a745'; // Success green
} else {
input.style.borderColor = '#dc3545'; // Error red
errorSpan.style.display = 'block';
}
return isValid;
}

function calculatePercentile() {
var babyAgeWeeksInput = document.getElementById('babyAgeWeeks');
var babyWeightKgInput = document.getElementById('babyWeightKg');
var babySexSelect = document.getElementById('babySex');

var babyAgeWeeksError = document.getElementById('babyAgeWeeksError');
var babyWeightKgError = document.getElementById('babyWeightKgError');

var isValidAge = validateInput('babyAgeWeeks', 'babyAgeWeeksError', 0, 100); // Max 100 weeks for reasonable range
var isValidWeight = validateInput('babyWeightKg', 'babyWeightKgError', 0.1, 20); // Max 20kg for reasonable range

if (!isValidAge || !isValidWeight) {
return; // Stop calculation if inputs are invalid
}

var ageWeeks = parseFloat(babyAgeWeeksInput.value);
var weightKg = parseFloat(babyWeightKgInput.value);
var sexIndex = parseInt(babySexSelect.value);

var results = getApproximatePercentile(ageWeeks, weightKg, sexIndex);

var mainResultDiv = document.getElementById('mainResult');
var weightForAgeDiv = document.getElementById('weightForAge').querySelector('span');
var averageWeightDiv = document.getElementById('averageWeight').querySelector('span');
var differenceDiv = document.getElementById('weightDifference').querySelector('span');

var resultsContainer = document.getElementById('resultsContainer');
resultsContainer.style.display = 'block';

if (!isNaN(results.percentile)) {
mainResultDiv.textContent = results.percentile + '%';
weightForAgeDiv.textContent = results.weightForAge.toFixed(2) + ' kg';
averageWeightDiv.textContent = results.medianWeight.toFixed(2) + ' kg';
differenceDiv.textContent = results.difference.toFixed(2) + ' kg';

// Update table
document.getElementById('tableAge').textContent = ageWeeks.toFixed(0);
document.getElementById('tableWeight').textContent = weightKg.toFixed(2);
document.getElementById('tableMedianWeight').textContent = results.medianWeight.toFixed(2);
document.getElementById('tablePercentile').textContent = results.percentile.toFixed(0) + '%';

} else {
mainResultDiv.textContent = 'N/A';
weightForAgeDiv.textContent = '– kg';
averageWeightDiv.textContent = '– kg';
differenceDiv.textContent = '– kg';
// Update table
document.getElementById('tableAge').textContent = '–';
document.getElementById('tableWeight').textContent = '–';
document.getElementById('tableMedianWeight').textContent = '–';
document.getElementById('tablePercentile').textContent = '–%';
}

updateChart(); // Update the chart with new data
}

function resetCalculator() {
document.getElementById('babyAgeWeeks').value = '12';
document.getElementById('babyWeightKg').value = '6.0';
document.getElementById('babySex').value = '0'; // Default to Male

document.getElementById('babyAgeWeeksError').textContent = '';
document.getElementById('babyWeightKgError').textContent = '';
document.getElementById('babyAgeWeeks').style.borderColor = '#ccc';
document.getElementById('babyWeightKg').style.borderColor = '#ccc';

document.getElementById('mainResult').textContent = '–%';
document.getElementById('weightForAge').querySelector('span').textContent = '– kg';
document.getElementById('averageWeight').querySelector('span').textContent = '– kg';
document.getElementById('weightDifference').querySelector('span').textContent = '– kg';

document.getElementById('tableAge').textContent = '–';
document.getElementById('tableWeight').textContent = '–';
document.getElementById('tableMedianWeight').textContent = '–';
document.getElementById('tablePercentile').textContent = '–%';

document.getElementById('copy-feedback').style.display = 'none';

// Reset chart data to initial state or default values
chartData.datasets[1].data = []; // Clear baby's weight data
updateChart(); // Re-render chart with reset data
}

function copyResults() {
var mainResult = document.getElementById('mainResult').textContent;
var weightForAge = document.getElementById('weightForAge').textContent;
var averageWeight = document.getElementById('averageWeight').textContent;
var difference = document.getElementById('weightDifference').textContent;
var age = document.getElementById('babyAgeWeeks').value;
var weight = document.getElementById('babyWeightKg').value;
var sex = document.getElementById('babySex').options[document.getElementById('babySex').selectedIndex].text;

var assumptions = "Key Assumptions:\n";
assumptions += "- Baby's Age: " + (age ? age + " weeks" : "N/A") + "\n";
assumptions += "- Baby's Weight: " + (weight ? weight + " kg" : "N/A") + "\n";
assumptions += "- Baby's Sex: " + sex + "\n";

var textToCopy = "Baby Weight Percentile Results:\n";
textToCopy += "——————————\n";
textToCopy += "Overall Percentile: " + mainResult + "\n";
textToCopy += weightForAge + "\n";
textToCopy += averageWeight + "\n";
textToCopy += difference + "\n";
textToCopy += "\n" + assumptions;

navigator.clipboard.writeText(textToCopy).then(function() {
var feedback = document.getElementById('copy-feedback');
feedback.style.display = 'block';
setTimeout(function() {
feedback.style.display = 'none';
}, 3000);
}).catch(function(err) {
console.error('Failed to copy: ', err);
alert('Failed to copy results. Please copy manually.');
});
}

// Initial calculation on page load if default values are present
document.addEventListener('DOMContentLoaded', function() {
// Ensure Chart.js is loaded before attempting to use it
if (typeof Chart !== 'undefined') {
// Initialize chart on load
updateChart();
// Perform an initial calculation if default values are set
calculatePercentile();
} else {
console.error("Chart.js library not loaded. Please include it in your HTML.");
}
});