Calculate your health profile using the Oxford "New BMI" formula.
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What is the Smart BMI?
The traditional Body Mass Index (BMI) formula, created in the 1830s, is simply weight divided by height squared. However, mathematicians at Oxford University developed the "Smart BMI" (or New BMI) to better account for how body mass scales in three dimensions. While standard BMI tends to make shorter people think they are thinner than they are and taller people think they are fatter than they are, the Smart BMI formula uses a power of 2.5 to provide a more accurate reflection of body composition.
The Science Behind the Calculation
The Smart BMI formula is calculated as follows: 1.3 × weight (kg) / height (m)2.5
This adjustment recognizes that we do not live in a two-dimensional world. As people get taller, their bone and muscle mass increase disproportionately to their height. By using a 2.5 exponent, the Smart BMI offers a modernized health metric that correlates more closely with body fat percentage across various heights.
Weight Categories Table
BMI Range
Category
Below 18.5
Underweight
18.5 – 24.9
Healthy Weight
25.0 – 29.9
Overweight
30.0 and Above
Obese
Real-Life Example
Consider an individual who is 190 cm (6'3″) tall and weighs 95 kg (210 lbs):
Standard BMI: 26.3 (Categorized as Overweight)
Smart BMI: 24.8 (Categorized as Healthy Weight)
In this case, the Smart BMI accounts for the natural skeletal and muscular volume required for a taller frame, suggesting the individual is within a healthy range rather than being overweight.
var currentUnit = 'metric';
function setUnits(unit) {
currentUnit = unit;
var weightLabel = document.getElementById('weightLabel');
var heightLabel = document.getElementById('heightLabel');
var weightInput = document.getElementById('weightInput');
var heightInput = document.getElementById('heightInput');
var mBtn = document.getElementById('metricBtn');
var iBtn = document.getElementById('imperialBtn');
if (unit === 'metric') {
weightLabel.innerText = 'Weight (kg)';
heightLabel.innerText = 'Height (cm)';
weightInput.placeholder = 'e.g. 75';
heightInput.placeholder = 'e.g. 180';
mBtn.className = 'active';
iBtn.className = ";
} else {
weightLabel.innerText = 'Weight (lbs)';
heightLabel.innerText = 'Height (inches)';
weightInput.placeholder = 'e.g. 165';
heightInput.placeholder = 'e.g. 70';
iBtn.className = 'active';
mBtn.className = ";
}
}
function calculateSmartBMI() {
var weight = parseFloat(document.getElementById('weightInput').value);
var height = parseFloat(document.getElementById('heightInput').value);
var resArea = document.getElementById('bmi-result-area');
var resVal = document.getElementById('resultValue');
var resCat = document.getElementById('resultCategory');
var resComp = document.getElementById('resultComparison');
if (!weight || !height || weight <= 0 || height <= 0) {
alert('Please enter valid positive numbers for weight and height.');
return;
}
var weightKg, heightM;
if (currentUnit === 'metric') {
weightKg = weight;
heightM = height / 100;
} else {
weightKg = weight * 0.453592;
heightM = height * 0.0254;
}
// Standard BMI
var standardBmi = weightKg / (heightM * heightM);
// Smart BMI (New BMI formula: 1.3 * weight / height^2.5)
var smartBmi = 1.3 * weightKg / Math.pow(heightM, 2.5);
resArea.style.display = 'block';
resVal.innerText = smartBmi.toFixed(1);
var category = "";
var color = "";
if (smartBmi < 18.5) {
category = "Underweight";
color = "#3498db";
} else if (smartBmi < 25) {
category = "Healthy Weight";
color = "#27ae60";
} else if (smartBmi < 30) {
category = "Overweight";
color = "#f39c12";
} else {
category = "Obese";
color = "#e74c3c";
}
resCat.innerText = category;
resCat.style.color = color;
resArea.style.backgroundColor = color + "15"; // Very light tint of category color
resArea.style.border = "2px solid " + color;
resComp.innerHTML = "Your Smart BMI is " + smartBmi.toFixed(1) + ". " +
"For comparison, your traditional BMI is " + standardBmi.toFixed(1) + ". " +
"The Smart BMI provides a more accurate scale for your specific height.";
resArea.scrollIntoView({ behavior: 'smooth', block: 'nearest' });
}