who calculator weight: WHO Weight-for-Age Analysis
This who calculator weight helps parents, clinicians, and analysts compare a child's weight against World Health Organization growth standards, delivering instant z-scores, percentiles, healthy ranges, and an explanatory chart in a professional single-column layout.
WHO Weight-for-Age Calculator
Enter age from birth to 60 months for the who calculator weight analysis.
Please enter an age between 0 and 60 months.
Use kilograms so the who calculator weight aligns with WHO reference data.
Please enter a weight between 1 and 30 kg.
Male
Female
Select the sex to pull the correct who calculator weight growth standard.
Please choose a sex.
Percentile: — | Status: —
Z-Score: —
Healthy Range (5th-95th): —
WHO Median Weight: —
Weight-for-Age Category: —
Formula: (Weight – WHO median) / WHO SD = Z-Score; Percentile derived from Z-Score using normal distribution.
WHO Reference Table for who calculator weight
Age (months)
Median (kg)
5th Percentile (kg)
95th Percentile (kg)
Series: WHO Median (blue line) | Child Weight (green line)
What is who calculator weight?
The who calculator weight is a WHO weight-for-age tool that compares a child's mass to standardized curves, giving caregivers a clear percentile benchmark. Parents use the who calculator weight to see if growth is tracking typical patterns. Clinicians use the who calculator weight to screen for undernutrition or rapid gain. A common misconception is that the who calculator weight is a diet tool for adults; it strictly maps child weight to age-specific norms.
Another misconception about the who calculator weight is that it predicts future height. The who calculator weight strictly evaluates current weight relative to peers. Because the who calculator weight draws from WHO growth standards, its focus is on global pediatric data rather than localized charts.
who calculator weight Formula and Mathematical Explanation
The who calculator weight uses a z-score approach: subtract the WHO median weight for the exact age from the child's weight, then divide by the WHO standard deviation. This who calculator weight formula converts raw kilograms into a standardized score, making different ages comparable. The who calculator weight then transforms the z-score into a percentile through the normal cumulative distribution.
Step 1: Identify WHO median weight for age and sex. Step 2: Find WHO standard deviation. Step 3: Apply z = (observed – median) / SD. Step 4: Convert z to percentile. The who calculator weight also computes 5th and 95th percentile thresholds to form a healthy range.
Variables in the who calculator weight computation
Variable
Meaning
Unit
Typical Range
Age
Child age used by who calculator weight
months
0-60
Weight
Observed mass for who calculator weight
kg
1-30
Median
WHO expected median weight
kg
3-18
SD
WHO standard deviation
kg
0.5-1.3
Practical Examples (Real-World Use Cases)
Example 1: A 10-month-old boy weighs 8.3 kg. The who calculator weight pulls the median of 8.6 kg and SD of 0.95 kg, yielding z = (8.3-8.6)/0.95 = -0.32. The who calculator weight percentile lands near the 37th percentile, showing healthy but slightly below midpoint growth.
Example 2: A 24-month-old girl weighs 14 kg. The who calculator weight references a median of 11.5 kg and SD of 1.1 kg. Z = (14-11.5)/1.1 = 2.27. The who calculator weight percentile surpasses the 98th percentile, signaling rapid gain that may need nutrition review.
How to Use This who calculator weight Calculator
Enter age in months, weight in kilograms, and select sex. The who calculator weight instantly updates the percentile, z-score, and healthy range. Review the primary result banner to see the percentile and status. Intermediate cards show the z-score and WHO median so the who calculator weight context is transparent.
Use the table to see reference points, and the chart to compare the who calculator weight result against the WHO curve. Copy results to share with a pediatrician. Reset returns sensible defaults for a quick new who calculator weight run.
Key Factors That Affect who calculator weight Results
Data accuracy: Precise kilograms and exact age ensure the who calculator weight outputs a reliable z-score.
Sex-specific curves: Selecting the correct sex aligns the who calculator weight with the right WHO standard.
Measurement timing: Weighing after meals or with clothes can skew the who calculator weight percentile upward.
Health conditions: Acute illness or hydration levels can shift the who calculator weight reading temporarily.
Nutrition quality: Balanced intake influences trends the who calculator weight will capture over months.
Socioeconomic context: Access to health services shapes patterns the who calculator weight may reveal.
Frequently Asked Questions (FAQ)
Is the who calculator weight for adults? No, the who calculator weight is calibrated for children 0-60 months.
How often should I use the who calculator weight? Monthly checks help track trends without overreacting to daily swings.
Does the who calculator weight replace medical advice? The who calculator weight is a guide; clinicians interpret results clinically.
What if the who calculator weight shows underweight? Consult a pediatrician to review feeding and health factors.
Can the who calculator weight handle preterm infants? Adjusted age should be used before inputting into the who calculator weight.
Why do boys and girls differ in the who calculator weight? WHO standards differ by sex, so the who calculator weight uses distinct curves.
Is percentile the same as z-score in the who calculator weight? The who calculator weight converts z-score to percentile; they are related but distinct.
Can I export who calculator weight results? Use the Copy Results button to share who calculator weight findings.
Related Tools and Internal Resources
{related_keywords} – Companion guide that complements the who calculator weight with deeper WHO growth insights.
{related_keywords} – Trend tracker aligned with who calculator weight outputs.
{related_keywords} – Nutrition checklist to pair with who calculator weight readings.
{related_keywords} – Hydration monitor that contextualizes who calculator weight changes.
{related_keywords} – Pediatric visit planner tied to who calculator weight milestones.
{related_keywords} – FAQ archive extending the who calculator weight knowledge base.
var maleData=[{age:0,median:3.3,sd:0.55},{age:6,median:7.9,sd:0.9},{age:12,median:9.6,sd:1.0},{age:18,median:10.9,sd:1.05},{age:24,median:12.2,sd:1.1},{age:36,median:14.3,sd:1.2},{age:48,median:16.3,sd:1.25},{age:60,median:18.3,sd:1.3}];
var femaleData=[{age:0,median:3.2,sd:0.5},{age:6,median:7.3,sd:0.85},{age:12,median:8.9,sd:0.95},{age:18,median:10.2,sd:1.0},{age:24,median:11.5,sd:1.1},{age:36,median:13.9,sd:1.2},{age:48,median:15.9,sd:1.25},{age:60,median:17.9,sd:1.3}];
var chartCtx=document.getElementById("weightChart").getContext("2d");
function resetCalc(){
document.getElementById("childAge").value=12;
document.getElementById("childWeight").value=9;
document.getElementById("childSex").value="male";
calculate();
}
function validateInputs(){
var age=parseFloat(document.getElementById("childAge").value);
var weight=parseFloat(document.getElementById("childWeight").value);
var sex=document.getElementById("childSex").value;
var valid=true;
if(isNaN(age)||age60){document.getElementById("ageError").style.display="block";valid=false;}else{document.getElementById("ageError").style.display="none";}
if(isNaN(weight)||weight30){document.getElementById("weightError").style.display="block";valid=false;}else{document.getElementById("weightError").style.display="none";}
if(sex!=="male"&&sex!=="female"){document.getElementById("sexError").style.display="block";valid=false;}else{document.getElementById("sexError").style.display="none";}
return valid;
}
function getInterpolated(age,data){
var i;
for(i=0;i=data[i].age&&age<=data[i+1].age){
var span=data[i+1].age-data[i].age;
var ratio=(age-data[i].age)/span;
var median=data[i].median+(data[i+1].median-data[i].median)*ratio;
var sd=data[i].sd+(data[i+1].sd-data[i].sd)*ratio;
return {median:median,sd:sd};
}
}
if(age0){prob=1-prob;}
return prob;
}
function formatNumber(n){return Math.round(n*100)/100;}
function calculate(){
if(!validateInputs()){
document.getElementById("primaryResult").textContent="Percentile: — | Status: –";
document.getElementById("zScoreBox").textContent="Z-Score: –";
document.getElementById("rangeBox").textContent="Healthy Range (5th-95th): –";
document.getElementById("medianBox").textContent="WHO Median Weight: –";
document.getElementById("categoryBox").textContent="Weight-for-Age Category: –";
return;
}
var age=parseFloat(document.getElementById("childAge").value);
var weight=parseFloat(document.getElementById("childWeight").value);
var sex=document.getElementById("childSex").value;
var data=sex==="male"?maleData:femaleData;
var interp=getInterpolated(age,data);
var median=interp.median;
var sd=interp.sd;
var z=(weight-median)/sd;
var percentile=Math.round(normalCDF(z)*1000)/10;
var p5=median+sd*(-1.645);
var p95=median+sd*(1.645);
var status;
if(z2){status="Above Healthy Range";}
else{status="Within Healthy Range";}
document.getElementById("primaryResult").textContent="Percentile: "+percentile+"th | Status: "+status;
document.getElementById("zScoreBox").textContent="Z-Score: "+formatNumber(z);
document.getElementById("rangeBox").textContent="Healthy Range (5th-95th): "+formatNumber(p5)+" kg to "+formatNumber(p95)+" kg";
document.getElementById("medianBox").textContent="WHO Median Weight: "+formatNumber(median)+" kg | SD: "+formatNumber(sd);
document.getElementById("categoryBox").textContent="Weight-for-Age Category: "+status;
document.getElementById("formulaNote").textContent="Formula: (Weight – "+formatNumber(median)+" kg) / "+formatNumber(sd)+" kg = Z-Score "+formatNumber(z)+"; Percentile from normal distribution ≈ "+percentile+"th.";
populateTable(data);
drawChart(data,weight);
}
function populateTable(data){
var body=document.getElementById("referenceTableBody");
body.innerHTML="";
for(var i=0;i<data.length;i++){
var row=document.createElement("tr");
var p5=data[i].median+data[i].sd*(-1.645);
var p95=data[i].median+data[i].sd*(1.645);
row.innerHTML="
"+data[i].age+"
"+formatNumber(data[i].median)+"
"+formatNumber(p5)+"
"+formatNumber(p95)+"
";
body.appendChild(row);
}
}
function drawChart(data,weight){
var ctx=chartCtx;
var w=ctx.canvas.width;
var h=ctx.canvas.height;
ctx.clearRect(0,0,w,h);
ctx.fillStyle="#ffffff";
ctx.fillRect(0,0,w,h);
var padding=50;
var maxAge=data[data.length-1].age;
var maxWeight=0;
var minWeight=100;
var i;
for(i=0;imaxWeight){maxWeight=data[i].median;}
if(data[i].medianmaxWeight){maxWeight=weight;}
if(weight<minWeight){minWeight=weight;}
maxWeight+=2;
minWeight=Math.max(0,minWeight-1);
ctx.strokeStyle="#cfd6df";
ctx.lineWidth=1;
for(i=0;i<=5;i++){
var y=padding+(h-2*padding)*(i/5);
ctx.beginPath();
ctx.moveTo(padding,y);
ctx.lineTo(w-padding,y);
ctx.stroke();
}
ctx.strokeStyle="#cfd6df";
for(i=0;i<=5;i++){
var x=padding+(w-2*padding)*(i/5);
ctx.beginPath();
ctx.moveTo(x,padding);
ctx.lineTo(x,h-padding);
ctx.stroke();
}
ctx.strokeStyle="#004a99";
ctx.lineWidth=2;
ctx.beginPath();
for(i=0;i<data.length;i++){
var px=padding+(w-2*padding)*(data[i].age/maxAge);
var py=h-padding-(h-2*padding)*((data[i].median-minWeight)/(maxWeight-minWeight));
if(i===0){ctx.moveTo(px,py);}else{ctx.lineTo(px,py);}
}
ctx.stroke();
ctx.strokeStyle="#28a745";
ctx.lineWidth=2;
ctx.beginPath();
for(i=0;i<data.length;i++){
var px2=padding+(w-2*padding)*(data[i].age/maxAge);
var py2=h-padding-(h-2*padding)*((weight-minWeight)/(maxWeight-minWeight));
if(i===0){ctx.moveTo(px2,py2);}else{ctx.lineTo(px2,py2);}
}
ctx.stroke();
ctx.fillStyle="#004a99";
ctx.font="12px Arial";
ctx.fillText("Age (months)",w/2-30,h-10);
ctx.save();
ctx.translate(15,h/2+20);
ctx.rotate(-Math.PI/2);
ctx.fillText("Weight (kg)",0,0);
ctx.restore();
}
function copyResults(){
var age=document.getElementById("childAge").value;
var weight=document.getElementById("childWeight").value;
var sex=document.getElementById("childSex").value;
var primary=document.getElementById("primaryResult").textContent;
var z=document.getElementById("zScoreBox").textContent;
var range=document.getElementById("rangeBox").textContent;
var median=document.getElementById("medianBox").textContent;
var text="who calculator weight results:\nAge: "+age+" months\nWeight: "+weight+" kg\nSex: "+sex+"\n"+primary+"\n"+z+"\n"+range+"\n"+median;
if(navigator.clipboard&&navigator.clipboard.writeText){navigator.clipboard.writeText(text);}else{
var textarea=document.createElement("textarea");
textarea.value=text;
document.body.appendChild(textarea);
textarea.select();
document.execCommand("copy");
document.body.removeChild(textarea);
}
}
calculate();